Hemodynamic evaluation of descending aortomyoplasty versus intra-aortic balloon pump performed in normal animals: an acute study.

OBJECTIVE: Aortomyoplasty is a surgical procedure that aims to induce hemodynamic benefits similar to those of the intra-aortic-balloon-pump (IABP). The objective of this study was to compare the coronary blood flow augmentation and afterload reduction produced by IABP and descending aortomyoplasty counterpulsation. METHODS: From a series of fifteen mongrel dogs (18-35 kg), eight underwent acute descending aortomyoplasty and seven had IABP application. Left anterior descending (LAD) coronary artery blood flow was measured using a Doppler flow probe. Left ventricular pressure in addition to aortic pressures both proximal and distal to either the aortomyoplasty site or the IABP position were monitored continuously. All experiments were acute and performed in normal hearts. RESULTS: Descending aortomyoplasty induced a 27% increase in the LAD blood flow integral during assisted beats (14.0+/-6 ml/min integral compared to 10.8+/-4 ml/min integral in unassisted beats [P<0.001]). This was comparable to an 18% rise in the LAD blood flow integral during IABP counterpulsation (from 8.6+/-3 ml/min to 10.2+/-4 ml/min [P<0.001]). Conversely, while IABP counterpulsation reduced the left ventricular afterload by 16% (from 102+/-23 mmHg to 86+/-26 mmHg [P<0.001]), descending aortomyoplasty did not result in afterload reduction. CONCLUSIONS: Descending aortomyoplasty produces coronary blood flow augmentation comparable to that achieved by the IABP. This may be important for end-stage ischemic patients. However, afterload reduction achieved by the IABP was not reproduced during descending aortomyoplasty counterpulsation. The surgical technique of descending aortomyoplasty should be modified to attain afterload reduction, thus improving treatment for congestive heart failure patients.     

Update 2001: Dynamic descending thoracic aortomyoplasty: comparison with intraaortic balloon pump in a model of heart failure

As Originally Published in 1994: Dynamic Descending Thoracic Aortomyoplasty: Comparison With Intraaortic Balloon Pump in a Model of Heart Failure by Robert R. Lazzara, MD, Dennis R. Trumble, MS, and James A. Magovern, MD. Cardiothoracic Surgical Research, Allegheny-Singer Research Institute, Department of Surgery, Allegheny General Hospital, and Allegheny Campus, The Medical College of Pennsylvania, Pittsburgh, Pennsylvania

Descending thoracic aortomyoplasty (DTA) uses the latissimus dorsi muscle to compress the proximal descending thoracic aorta as an autogenous diastolic counterpulsator. We studied the hypothesis that DTA could confer hemodynamic benefits equivalent to those yielded by an intraaortic balloon pump (IABP) in dogs (n = 7) with heart failure. The left latissimus dorsi muscle was wrapped around the proximal thoracic aorta and subsequently electrically conditioned to induce fatigue resistance. Heart failure was produced by rapid ventricular pacing after muscle conditioning. Data were collected under three conditions: (1) after the induction of heart failure; (2) with the 20-mL IABP at 1:1; and (3) with the DTA stimulated at 1:1. Effective diastolic counterpulsation was achieved with both the IABP and the DTA. The mean diastolic aortic pressure increased from 66 ± 5 mm Hg at baseline to 90 ± 4 mm Hg with the IABP and to 75 ± 4 mm Hg with the DTA. The left ventricular peak and end-diastolic pressures decreased with IABP (95 ± 5 mm Hg versus 88 ± 4 mm Hg and 16 ± 4 mm Hg versus 12 ± 4 mm Hg, respectively; p < 0.05) and with DTA (95 ± 5 mm Hg versus 87 ± 4 mm Hg and 16 ± 4 mm Hg versus 12 ± 4 mm Hg, respectively; p < 0.05). Counter-pulsation with the IABP did not change the end-systolic pressure–volume relationship or the time constant for diastolic relaxation, whereas the DTA increased the end-systolic pressure-volume relationship (3.2 ± 0.6 mm Hg/mL versus 4.0 ± 0.7 mm Hg/mL; p < 0.05) and decreased the time constant for diastolic relaxation (49 ± 5 msec versus 45 ± 6 msec; p < 0.05). These data show that DTA using conditioned skeletal muscle can provide diastolic counterpulsation in animals with compromised cardiac function. In addition, the procedure appears to have an effect on left ventricular contractility that is independent of its effects on cardiac preload and afterload.     

ITA versus SVG: a comparison of instantaneous pressure and flow dynamics during competitive flow

Objective: Competitive flow from patent native coronary vessels is implicated in the failure of internal thoracic artery (ITA) grafts, but it is not thought to affect saphenous vein graft (SVG) patency. This study examines instantaneous pressure and flow dynamics in left ITA and SVG grafts in competition with a patent left anterior descending (LAD) artery. Methods: SVG (3.0–4.0 mm) and ITA (1.5–2.0 mm) to proximal LAD (2.5–3.0 mm) coronary bypass was performed in 10 mongrel dogs. Flow and pressure were measured in the occluded (No Competition) and opened (Competition) ITA, SVG and LAD. Results: The ITA and SVG, when each was the sole inflow to the LAD, provided similar flow as the native LAD. During competitive flow, total LAD flow was preserved and flow in the ITA and SVG were reduced (8.20±1.25 and 10.00±1.73 ml/min; P<0.005). SVG diastolic flow was reduced to 11.52±2.17 ml/min (55.5%); P<0.003. Flow in the SVG remained predominantly antegrade. In contrast, ITA diastolic flow was reduced more drastically, to 5.37±1.25 ml/min (80.7%); P<0.0001. When the ITA was the only inflow to the LAD, there was delay in the LAD pressure wave. This delay disappears during competition due to the large, systolic retrograde flow up the ITA. Conclusion: The ITA, compared to the SVG, is a longer and narrower conduit with lower levels of flow during competition. Due to a delay in the pressure wave, the ITA flow is retrograde during early systole. Low levels of flow, with a markedly decreased diastolic phase, and the oscillating pattern in systole (retrograde/antegrade) may be poorly tolerated by the ITA endothelium and lead to graft deterioration.     

Evaluation of coronary bypass flow with color-Doppler and magnetic resonance imaging techniques: comparison with intraoperative flow measurements

Objectives: After coronary artery bypass surgery, patency and flow assessment is based on invasive methods such as angiography and intravascular ultrasound or flow wire techniques. The aim of the study was to compare intraoperative transit time flow measurements of coronary bypass grafts with early postoperative color-Doppler and MR-imaging assessment. Methods: In 22 patients (62±8.5 years) undergoing elective coronary bypass surgery the flow was measured in all internal mammary artery grafts (IMA) and saphenous vein grafts using the transit time flow technique. Postoperatively (days 5–7) all patients had a color-Doppler IMA graft assessment followed by a MR-angiography and flow measurement (navigator echo phase contrast technique with and without contrast bolus application) to determine patency and graft flow. Results: Data are expressed as the mean±SD). (1) In all patients the left IMA graft to the left anterior descending coronary artery (LAD) could be identified and flow could be assessed with both color-Doppler and MRI. Venous grafts could only be visualized by MRI. The use of an intravenous contrast bolus enhanced the visualization of coronary artery bypass grafts. (2) The mean IMA to LAD flow was 33±17 ml/min intraoperatively by transit time and postoperatively 36±25 ml/min by MR respectively 66±54 ml/min by color-Doppler technique. (3) The systolic/diastolic flow ratio was 0.44±0.12 intraoperatively and 0.43±0.17 postoperatively by MR respectively 0.67±1.0 by color-Doppler. (4) A statistically significant correlation could be demonstrated between intraoperative transit time and postoperative MR flow measurements (r=0.57; P<0.04), whereas the correlations to color-Doppler flow were poor. Postoperatively MR and color-Doppler showed a good correlation of systolic/diastolic flow ratio (r=0.88; P<0.008). Conclusions: The color-Doppler method during echocardiography and MR-imaging are useful non-invasive techniques to visualize postoperative IMA grafts for patency assessment. The quantification of IMA flow is still difficult with either technique, but MR flow measurements showed the best correlation to the intraoperatively measured transit time flow. The MR technique is the most promising non-invasive method for postoperative evaluation of coronary bypass grafts, since it allows visualization and reliable flow quantification.     

Impact of postoperative blood pressure control on regression of left ventricular mass following valve replacement for aortic stenosis

Objective: Considerable left ventricular (LV) hypertrophy sometimes remains after aortic valve replacement (AVR) for aortic stenosis. For this issue, most previous studies have focused solely on transprosthetic pressure gradient, although true problem is not the pressure gradient itself but an elevated LV pressure. This study investigated the impact of blood pressure on postoperative LV mass regression, which had been overlooked in previous studies. Methods: Seventy-nine adult patients with pure aortic stenosis who were treated with AVR using bileaflet mechanical valves underwent echocardiography before surgery, around 6 months later (‘early’), and 2–3 years later (31.7±14.7 months, ‘late’). Patients were divided into two groups whether postoperative systolic blood pressure was below (n=47; N group) or above 130 mmHg (n=32; H group) following recommendation of WHO-ISH and JNC 7th report. Preoperative LV mass (g/m²) did not differ significantly (232±80 vs. 243±76, P=0.91). Results: LV mass became significantly smaller and regression was significantly more effective in N group than in H group both at ‘early’ (145±43 vs. 180±54, regression against preoperative value 34.6±19.1 vs. 19.9±26.6%, P=0.007) and ‘late’ (132±41 vs. 178±51, regression 41.1±16.0 vs. 21.0±27.0%, P<0.001) evaluations. Regression between ‘early’ and ‘late’ evaluations was significant only in N group (P=0.012). The LV mass index returned to the normal range at ‘late’ evaluation in 52.1% of N group and 12.5% of H group patients (P<0.001), and 25 out of 29 patients without residual LV hypertrophy were N group patients. Multivariate analyses revealed that preoperative LV mass index (P<0.001) and postoperative systolic blood pressure (P=0.007) showed significant influence on postoperative LV mass index, and postoperative systolic blood pressure alone significantly (P<0.001) influenced the regression ratio of the LV mass against the preoperative value. No prosthesis related variables (size, orifice area index, pressure gradient) had significant influence. Conclusions: For LV mass regression after AVR, postoperative blood pressure appeared to be more important than prosthesis selection. Controlling the systolic blood pressure below 130 mmHg was beneficial, which coincided with recommendation of WHO-ISH and JNC 7th report despite the pressure drop due to prosthesis in the aortic position.     

Right ventricle-to-pulmonary artery shunt and modified Blalock–Taussig shunt in preparation to hemi-Fontan procedure in children with hypoplastic left heart syndrome

Objective: The advantageous effect of right ventricle-to-pulmonary artery shunt (RV–PA) on the early postoperative hemodynamics in the Norwood procedure for hypoplastic left heart syndrome (HLHS) is well known. Numerous controversies still exist with respect to the late consequences of this new palliation method in preparation for the second stage procedure. Methods: Between September 1997 and September 2004, a consecutive series of 78 children with HLHS from a single institution underwent the hemi-Fontan procedure: Group 1 (n=27) after Blalock–Taussig shunt (BT), and Group 2 (n=51) after RV–PA. Hemodynamic, echocardiographic and clinical perioperative data were analyzed. Results: There were no significant differences in the age and operative weight (Group 1: 6.9±1.04 months, 6.22±0.99 kg; Group 2: 6.57±1.12 months, 6.36±0.86 kg). Children after RV–PA were characterized by a significantly higher preoperative hematocrit value (P=0.014), lower aortic and superior vena cava oxygen blood saturation (P<0.001, P=0.024), severe right ventricle hypertrophy more rarely diagnosed in echocardiography (P<0.004), lower Qp:Qs ratio (P=0.011), larger right (P=0.001) and left (P=0.006) pulmonary artery index and a shorter intensive care unit stay after the hemi-Fontan procedure (P=0.004). Conclusions: The Norwood procedure with the RV–PA shunt provides satisfactory late hemodynamics and improves the development of the pulmonary arteries. Children with hypoplastic left heart syndrome subjected to this new method of palliation are good candidates for the hemi-Fontan procedure.     

Differences in LIMA Doppler characteristics for different LAD perfusion areas

Objectives: To correlate supraclavicular left internal mammary artery (LIMA) to left anterior descending artery (LAD) area Doppler characteristics with angiographically perfused area. Methods: Sixty patients (50 male, mean age 62±7.3 years) with LIMA to LAD area grafting were prospectively entered in a follow up study. Supraclavicular echo Doppler of the LIMA was studied at the LIMA origin preoperatively, and at 4.8±3.8 months and 1.8±0.9 years postoperatively. The potential area to be revascularized judged from preoperative angiography was called the ‘target’ area. Control angiography (native and LIMA) was done at 1.5±0.9 years. The perfused area % was classified into group I ≤17.0% (n=16), group II >17.0% and <22.50% (n=17), and group III ≥22.50% (n=18) and related to LIMA Doppler characteristics. Multivariate linear regression analyses (MLRA) were performed to assess the relations between Doppler variables and the perfused area, target area and ratio of perfused/target area. Results: At MLRA perfused area was significantly related to the natural logarithm of diastolic peak velocity (DPV) (P=0.013) and diastolic mean velocity (P=0.048) and the ratio only to the degree of LAD stenosis (P=0.004). In hyperaemic response maximal DPV (DPV max) showed significant correlation to the perfused area (P=0.005) as well as to the ratio (P=0.017). When analyzing the additive power of both investigations, only DPV max (P=0.005) correlated significantly to the perfused area and for the ratio only the degree of stenosis of the LAD emerged as significant (P=0.004). Conclusions: At MLRA the diastolic flow pattern at rest and the maximal DPV in hyperaemic response correlated significantly with the LIMA run-off area whereas the last variable is the strongest predictor of the LIMA run-off area.     

Acute descending aortomyoplasty induces coronary blood flow augmentation

BACKGROUND: Aortomyoplasty is a procedure aimed to improve cardiac output in patients suffering from heart failure. Stimulation of the latissimus dorsi muscle around the aorta produces hemodynamic effects similar to those of the intraaortic balloon pump. These may be maintained without the accompanying complications or the need for anticoagulation. The objective of this study was to test the acute effects of aortomyoplasty on coronary artery blood flow. METHODS: Eight mongrel dogs (18 to 30 kg) underwent acute descending aortomyoplasty. Several stimulation protocols were applied after wrapping of the latissimus dorsi muscle around the aorta in different surgical configurations. The left anterior descending coronary blood flow was measured using a transonic Doppler flow probe. Left ventricular and aortic pressures, proximal and distal to the aortomyoplasty site, were monitored continuously. RESULTS: Significant aortic diastolic pressure augmentation was expressed both as an increase in peak values, from 110 +/- 24 mm Hg to 120 +/- 24 mm Hg (p < 0.001) and as an increase in the diastolic integral, from 64 +/- 23 mm Hg x s to 84 +/- 37 mm Hg x s (p < 0.001). Concomitantly, peak left anterior descending coronary blood flow increased from 26 +/- 10 mL/min to 32 +/- 12 mL/min (p < 0.001). This was associated with an increase in the diastolic flow integral from 11 +/- 4 mL to 14 +/- 6 mL (p < 0.001). CONCLUSIONS: Descending aortomyoplasty induces significant augmentation of coronary blood flow. Optimal timing of muscle stimulation is important in achieving the best assist. This procedure may prove beneficial for end-stage ischemic patients.     

Intraaortic Balloon Counterpulsation Improves Right Ventricular Failure Resulting From Pressure Overload

Background. Right ventricular (RV) dysfunction is common after heart transplantation, and myocardial ischemia is considered to be a significant contributor. We studied whether intraaortic balloon counterpulsation would improve cardiac function using a model of acute RV pressure overload.

Methods. In 10 anesthetized sheep, RV failure was induced using a pulmonary artery constrictor. Baseline measurements included mean systemic blood pressure, RV peak systolic pressure, cardiac index, and RV ejection fraction. Myocardial and organ perfusion were measured using radioactive microspheres.

Results. After pulmonary artery constriction, there was an increase in RV peak systolic pressure (32 ± 2 to 60 ± 3 mm Hg; p < 0.01) and a decrease in mean systemic blood pressure (68 ± 4 to 49 ± 2 mm Hg; p < 0.01), RV ejection fraction (0.51 ± 0.04 to 0.16 ± 0.02; p < 0.01), and cardiac index (2.48 ± 0.04 to 1.02 ± 0.11; p < 0.01). Blood flow to the RV did not change significantly, but there was a significant reduction in blood flow to the left ventricle. The initiation of intraaortic balloon counterpulsation (1:1) using a 40-mL intraaortic balloon inserted through the left femoral artery resulted in an increase in mean systemic blood pressure (49 ± 2 to 61 ± 3 mm Hg; p < 0.01), cardiac index (1.02 ± 0.11 to 1.45 ± 0.14; p < 0.05), RV ejection fraction (0.16 ± 0.02 to 0.23 ± 0.02; p < 0.01), and blood flow to the left ventricle.

Conclusions. In a model of right heart failure, the institution of intraaortic balloon counterpulsation caused a significant improvement in cardiac function. Although RV ischemia was not demonstrated, the augmentation of left coronary artery blood flow by intraaortic balloon counterpulsation and subsequent improvement in left ventricular function suggest that left ventricular ischemia contributes to RV dysfunction, presumably through a ventricular interdependence mechanism. Therefore, study of the safety and efficacy of intraaortic balloon counterpulsation in the management of patients with acute right heart dysfunction is warranted.     

The warm versus cold perfusion controversy: a clinical comparative study

To evaluate the effects of temperature on myocardial and total body protection, we analyzed 129 consecutive patients who underwent coronary artery bypass grafting, valve replacement, or both, with continuous cardioplegia (Cp). The patients were assigned to three groups: group I (n = 37) normothermic cardiopulmonary bypass (CPB) (37°C) and warm (37°C) Cp, group II (n = 49) normothermic CPB and cold (4°C) Cp and group III (n = 43) hypothermic (28°C) CPB and cold Cp. Comparison of groups I and II showed similar serum levels of creatine kinase (CK) and its myocardialspecific isoenzyme on the first postoperative day, a similar rate of perioperative myocardial infarction, postoperative need for intra-aortic balloon pump, postoperative need for inotropic support and mortality. Comparison of groups I and III showed similar serum levels of CK, amylase, lactate dehydrogenase and creatinine on the first postoperative day, a similar complication rate and mortality rate. However, normothermic CPB resulted in a shorter bypass time (83 ± 4 vs 98 ± 7 min, P<0.05) and interval until extubation (25.0 ± 3.8 vs 40.3 ± 7.4 h, P<0.05). In conclusion, there are no differences concerning myocardial protection, however, warm CPB shortens the perfusion time and postoperative course.     

Downsizing of the mitral valve and coronary revascularization in severe ischemic mitral regurgitation results in reverse left ventricular and left atrial remodeling

Objective: Data of combined mitral downsizing by restrictive prosthetic ring annuloplasty and coronary artery bypass grafting (CABG) in patients with ischemic cardiomyopathy and moderately severe to severe mitral regurgitation (MR) are rare, and little is known about the effect on reverse left ventricular (LV) and left atrial (LA) remodeling. Methods: Thirty-eight patients (70.6±8.3 years) with coronary artery disease, ischemic cardiomyopathy (LV ejection fraction [LVEF] 31±8%) and moderately severe to severe MR (grade 3.6±0.5) underwent CABG and mitral downsizing by 2–4 ring sizes. Clinical follow-up and serial transthoracic echocardiographic studies were performed after surgery (discharge, 3±0.5 months, 13±7 months) to assess survival, NYHA class, MR, leaflet coaptation height, LA and LV dimensions/volumes, fractional shortening (FS) and LVEF. Results: Early mortality (<30 days) was 2.6%, survival at follow-up was 92 and 85%, respectively. NYHA class improved from 3.3±0.6 to 1.5±0.6 (P<0.001). Residual MR at discharge and at follow-up was grade 0.5 and 0.6, respectively (P<0.001). Leaflet coaptation height was 8±1 mm and did not change over time. LV end-diastolic, end-systolic and LA dimensions decreased from 60±7 to 57±8 mm, from 47±9 to 42±9 mm and from 51±5 to 45±4 mm, FS increased from 23±9 to 28±10% (P<0.001); LV end-diastolic and end-systolic volumes decreased from 188±33 to 171±30 ml and from 129±35 to 105±33 ml, LVEF increased from 31±8 to 39±10% (P<0.001). Conclusions: Combined mitral downsizing and CABG surgery was performed with excellent clinical results: only minimal residual MR, a significant reduction of LA dimension and an increase of LV contractility due to reverse remodeling were observed.     

Respiratory dysfunction after coronary artery bypass grafting employing bilateral internal mammary arteries: the influence of intact pleura

Objective: To evaluate the role of intact pleurae regarding the postoperative respiratory functional status in patients undergoing coronary revascularization employing both internal mammary arteries (IMAs), according to the pedunculated or skeletonized technique (SKT) with opened or intact pleurae. Materials and methods: Using both IMAs, 299 patients underwent elective coronary revascularization. They were randomized and divided into group I (n=82, undergoing IMA harvesting according to the SKT without opening the pleurae); group II (n=186, undergoing IMA harvesting according the pedunculated technique with open pleurae); and group III (n=31, undergoing IMA harvesting according the SKT with incidentally opened pleurae). There were no differences regarding the preoperative patient characteristics and the anaesthetic and surgical management. Results: There were two deaths in group I versus seven in group II and one in group III (P=ns). The number of total arterial myocardial revascularization and arterial composite grafts was significantly higher in groups I and III than in group II, (P<0.001 and P<0.005, respectively). The incidence of postoperative complications was similar between groups. Blood loss of >1000 ml was significantly higher in group II than group I (P<0.028); but the incidence of re-thoracotomy and blood transfusion was similar between groups. The mechanical ventilation time was significantly higher in groups II and III versus group I (P<0.018 and P<0.02, respectively). The incidence of prolonged ventilation (>24 h), pleural effusion, thoracocentesis and atelectasis, resulted in being significantly higher in group II than group I. The incidence of thoracocentesis was significantly higher in group III than group I. The pain score and analgesic requirements at 1–12 h after awakening were significantly higher in groups II and III versus group I, becoming similar after the chest tubes were removed. PaO₂ was significantly higher, and PaCO₂ and FiO₂ were significantly lower in group I than groups II and III at 1 and 4 h before extubation and at 1 and 4 h after extubation. PaO₂ and PaCO₂ became similar between groups at the 5th postoperative day. Conclusions: According to our results, we may conclude that pleural integrity has beneficial effects on the respiratory functional status after coronary revascularization using both IMAs. A meticulous and more careful IMA harvesting approach significantly reduces the postoperative morbidity regarding the pulmonary functional status, and as a consequence, reduces the hospital costs.     

Prospective randomized trial of single clamp technique versus intermittent ischaemic arrest: myocardial and neurological outcome

Objective: To explore the hypothesis that intermittent ischaemic arrest (IIA) provides better myocardial preservation but generates a larger number of cerebral microemboli (ME) and consequently a higher incidence of post-operative cerebral dysfunction compared with the single clamp technique (SCT). Methods: Ninety-one patients with stable angina undergoing elective CABG with no clinical evidence of aortic or cerebro-vascular or neurological disease were prospectively randomized to: IIA (n=43) or SCT with intermittent anterograde cold blood cardioplegia (n=48). Myocardial preservation was assessed by measuring serum CK-MB, Troponin-T (TnT) and Troponin-I (TnI) and from pre- and post-operative ECGs and left ventricular (LV) function by echocardiography. Intra-operative cerebral ME were counted by transcranial Doppler of the right middle cerebral artery. All patients completed the Luria Nebraska Neuropsychological Battery (LNNB) tests for motor, visual, reading, memory and intellectual processes the day before surgery and at 1 week and 6 months post-operatively. Serum levels of the neuro-specific protein S-100 were measured. Results: The two groups were comparable for age, sex, extent of coronary disease, previous myocardial infarction, diabetes, hypertension and number of arterial and venous grafts. The median number of ME detected per patient was 34 (range 4–208) and was similar in both groups. Protein S-100 levels remained normal and similar in both groups at all times except in one patient with SCT who had an operative stroke. LNNB scores were similarly depressed at 1 week and recovered in all cases at 6 months. There was no correlation between the number of ME and LNNB scores. Median peak TnI levels were 0.64 μg/l with IIA vs. 0.87 μg/l with SCT (P=NS) and TnT 0.8 μg/l vs. 1.08 μg/l (P<0.03). SCT was however associated with longer mean ischaemic (67.6±16.1 vs. 34.5±16.5 min, P<0.001) and mean bypass time (88.5±18.2 vs. 74.6±26.3min, P<0.004) than IIA. Four patients with SCT and none with IIA had ECG changes suggestive of MI (P=0.04). Conclusion: During elective CABG in patients with no clinical evidence of aortic or cerebro-vascular disease the incidence of peri-operative ME and post-operative neuropsychological disturbances are comparable with both techniques of myocardial preservation. Biochemical analysis suggests that IIA provides more effective myocardial preservation.     

Pyruvate/dichloroacetate supply during reperfusion accelerates recovery of cardiac energetics and improves mechanical function following cardioplegic arrest

Objectives: Cardioplegic arrest during cardiac surgery induces severe abnormalities of the pyruvate metabolism, which may affect functional recovery of the heart. We aimed to evaluate the effect of pyruvate and dichloroacetate administration during reperfusion on recovery of mechanical function and energy metabolism in the heart subjected to prolonged cardioplegic arrest. Methods: Four groups of rat hearts perfused in working mode were subjected to cardioplegic arrest (St. Thomas’ No. 1), 4 h of ischaemia at 8°C and reperfusion with either Krebs buffer alone (C) or with 2.8 mM pyruvate (P), with 1 mM dichloroacetate (D), or with a combination of both (PD). Mechanical function was recorded before cardioplegic arrest and at the end of experiments. In groups C and PD, additional experiments were performed using ³¹P nuclear magnetic resonance spectroscopy in non-working Langendorff mode to evaluate cardiac high-energy phosphate concentration changes throughout the experiment. Results: Improved recovery of cardiac output (% of the preischaemic value±SEM, n=9–12) was observed in all three treated groups (65.7±4.3, 59.5±5.2 and 59.5±5.3% in PD, P and D, respectively) as compared with C (42.2±4.6%; P<0.05). Recovery of coronary flow was improved from 66.4±3.8 in C to 94.9±8.6% in PD (P<0.05). The phosphocreatine recovery rate in the first minutes of reperfusion was increased from 9.9±1.5 in C to 31.5±4.3 μmol/min per g dry wt in PD (P<0.001). No differences were observed in ATP or phosphocreatine concentrations at the end of experiment. Conclusions: The administration of pyruvate and dichloroacetate improves the recovery of mechanical function following hypothermic ischaemia. Accelerated restoration of the energy equilibrium in the initial phase of reperfusion may underlie the metabolic mechanism of this effect.     

Inhibition of myosin light chain kinase provides prolonged attenuation of radial artery vasospasm

Objective: Current treatments for conduit vessel vasospasm are short-acting and do not inhibit all vasospastic stimuli. This study tests the hypothesis that irreversible inactivation of myosin light chain kinase provides sustained inhibition of arterial vasoconstriction stimulated by a spectrum of vasopressors. Methods: Canine radial artery segments were soaked for 60 min in control buffer or buffer with wortmannin, an irreversible inhibitor of myosin light chain kinase. The vessels were then thoroughly washed and contractile responses were quantified in response to a spectrum of vasopressors at 2 and 48 h after treatment. After 48 h, selected vessels were examined for morphologic changes and development of apoptosis. Results: Two hours after treatment, wortmannin-soaked vessels contracted significantly less than controls in response to norepinephrine (0.19±0.07 g vs. 7.22±0.37 g, P<0.001), serotonin (0.92±0.35 g vs. 9.64±0.67 g, P<0.001), thromboxane-mimetic U46619 (1.25±0.17 g vs. 10.99±0.50 g, P<0.001), and KCl (1.98±0.27 g vs.15.00±0.48 g, P<0.001). At 48 h, vasoconstriction remained significantly inhibited in wortmannin-treated vessels compared to control vessels in response to norepinephrine (2.36±0.17 vs. 6.95±0.47 g, P<0.001), serotonin (4.67±0.39 vs. 12.42±0.70 g, P<0.001), U46619 (5.42±0.34 vs. 9.29±0.74 g, P=0.008), and KCl (7.49±0.48 vs. 13.32±0.60 g, P<0.001). Histology of wortmannin-treated vessels revealed no overt smooth muscle or endothelial cell damage. TUNEL staining revealed a significantly greater proportion of apoptotic smooth muscle and endothelial cells in wortmannin-treated vessels as compared to controls. Conclusions: Disengaging the smooth muscle contractile apparatus by irreversibly binding myosin light chain kinase with wortmannin significantly attenuates radial artery vasoconstriction up to 48 h after brief treatment. This novel strategy may prevent vasospasm of arterial grafts from all causes for several postoperative days.     

Aprotinin reduces postoperative bleeding and the need for blood products in thoracic surgery: results of a randomized double-blind study

Objective: Bleeding complications have been a major concern in certain thoracic surgery operations, especially decortication and pulmonary resection for inflammatory pulmonary infection. Prevention of plasminogen activation and fibrinolysis by aprotinin administration has been shown to reduce perioperative bleeding during operations associated with high blood consumption. Methods: Use of blood products (packed red cells, whole blood), chest tube drainage, analgesic requirement, chest tube duration for the patients undergoing major thoracic operations were recorded. In a double blind randomized fashion, patients were assigned to two groups receiving aprotinin (n=51) at a loading dose of 10⁶ kallikrein inhibitory units (KIU) followed by an infusion of the same dose during chest closure or receiving placebo (n=52). On a daily basis, red-cell percentages of total fluid from drainage bottles were recorded and using the blood hematocrit level of the patient of the day before, the corrected value for the patient's blood volume equivalent of daily drainage was calculated. Results: There was a significant reduction in perioperative use of donor blood (0.98±0.92 vs. 0.45±0.32 unit; P=0.0026), and total chest tube drainage (corrected value for the corresponding blood volume) (28.2±36.9 vs. 76.9±53.3 ml, P=0.0004) (mean±standard deviation) in the aprotinin group. However, aprotinin did not reduce postoperative transfusion or decrease in hematocrit level due to thoracic operations. In high transfusion-risk thoracic surgery patients (patients who underwent decortication, pulmonary resection for inflammatory lung disease and chest wall resection), the perioperative transfusion was only 0.50±1.08 units in aprotinin group, compared with 1.94±0.52 units in control group (P=0.003). Postoperative transfusion was also reduced in aprotinin administrated group (0.53±0.56 vs. 1.38±0.97 units; P=0.02). The mean total blood loss was decreased to nearly one third of the blood loss of the control group (41±28 ml vs. 121±68 ml; P=0.001). Conclusion: Aprotinin significantly reduced perioperative transfusion requirement and postoperative bleeding during major thoracic operations. Aprotinin decreased perioperative transfusion needs. Moreover, patients who were at risk of greater blood loss during and after certain thoracic operations had a greater potential to benefit from prophylactic perioperative aprotinin treatment.     

An evaluation of the intraoperative transit time measurements of coronary bypass flow

Objective: The intraoperative measurement of the coronary bypass flow enables the identification of technical errors while the sternum is still open. The transit-time flow method is able to effectively measure the internal thoracic artery graft flow. The aim of the present study was to analyze the factors which affected the bypass flow rate. Methods: We measured the blood flow of 291 in situ internal thoracic artery (ITA) and 190 saphenous vein (SV) grafts constructed in 171 patients undergoing coronary artery bypass grafting from December 1996 to March 2000 using this method during the surgery. All patients underwent postoperative coronary angiography before the patients were discharged. The blood flow rate of all bypass grafts constructed was assessed after the patients were weaned from cardiopulmonary bypass. Results: The mean flow rate of all ITA grafts was 65.1±36.7 ml/min and that of all SV grafts was 56.4±29.9 ml/min. According to analyses using correlation tests, the graft flow was found to significantly correlate with the grafted perfusion areas and the diameter of the bypassed coronary arteries. However, no significant difference was observed between the flow rates of the ITA grafts with and without stenosis or string phenomenon, but significant (P<0.0001) correlation was observed between the occurrence of a string sign and the degree of proximal stenosis of the recipient coronary artery. Regarding SV grafts, the mean flow rate of occluded grafts (29.2±20.5 ml/min) was significantly (P<0.0001) less than non-occluded grafts (56.4±29.9 ml/min). Conclusions: The bypass flow was affected by such a large number of factors that only measuring the bypass flow rate could not sufficiently predict either stenosed or narrowed grafts. However, ITA grafts bypassed to the coronary arteries with less stenosis were shown to more easily become narrowed.     

Pulmonary preservation with Bretscheider''s HTK and Celsior solution in minipigs

Background: Pulmonary preservation with high potassium/low oncotic pressure Euro-Collins (EC) solution is associated with endothelial dysfunction and reduced surfactant function. We compared two low potassium solutions, histidine-tryptophane-ketoglutarate (HTK) and Celsior, to EC in lung ischemia-reperfusion injury. Methods: In 19 minipigs, the left lung was perfused in situ with cold preservation solution (EC, n=6; HTK, n=6; Celsior, n=7). Reperfusion was started after 90 min of warm ischemia. The right pulmonary artery and main bronchus were clamped. Bronchoalveolar lavage (BAL) was obtained before ischemia and after 2 h of reperfusion. Surfactant activity was determined from the BAL in a pulsating bubble surfactometer. Results: Animals in the EC group survived 3.7±1.4 h. Six Celsior and five HTK treated animals survived the observation period of 7 h (P<0.001). Compliance of the reperfused lung deteriorated less in both Celsior and HTK groups (P<0.001). In EC and HTK animals, the pO₂/FiO₂ ratio was lower (P=0.002), and pulmonary vascular resistance was higher (P=0.02) than in Celsior animals. Surfactant function was impaired after reperfusion in all groups. Conclusions: Compared to EC, HTK solution showed moderate and Celsior distinct improvement of post-ischemic pulmonary function. However, surfactant function was not well preserved in any group.     

Evaluation of preoperative intra-aortic balloon pump support in high risk coronary patients

Objective: The intra-aortic balloon pump (IABP) is an established additional support to pharmacological treatment of the failing heart after myocardial infarction, unstable angina and cardiac surgery. The effect of preoperative IABP in high risk patients was evaluated. Methods: Between June 1994 and March 1996 all high risk patients for CABG (two or more of these criteria: Left ventricular ejection fraction (LVEF) ≤40%, left main stem stenosis ≥70%, REDO-CABG, unstable angina) were randomized into either of 3 groups: (1) IABP 1 day prior to surgery, (2) IABP 1–2 h prior to CPB and (3) no preoperative IABP, controls. Exclusion criteria: cardiogenic shock preoperatively. Fifty-two patients have entered the study—group 1 (13 patients), group 2 (19 patients) and group 3 (20 patients). Preoperative patient characteristics and operative data revealed no group differences. There were 56% REDO's, unstable angina 59%, LVEF≤40%, 87% (34.0±11.6%) and left main stem stenosis in 35%. Results: The CPB-time was shorter in groups 1 and 2 88.7±20.3 min than in group 3 105.5±26.8 min, P<0.001, while ischemia time did not differ. Hospital mortality was higher in group 3, 25% vs. 6% (groups 1 and 2). Postoperative low cardiac output was seen in 12 patients (60%) in group 3 vs. 6 patients (19%) in groups 1 and 2, P<0.05. Cardiac index increased significantly prior to CPB in groups 1 and 2. After CPB cardiac index was significantly higher in groups 1 and 2 compared to Group 3 and continued to increase. The IABP was removed after 3.1±1.0 days in group 3 vs. 1.3±0.6 days in groups 1 and 2, P<0.001. In group 3, 11 patients required IABP postoperatively compared to only 4 patients in groups 1 and 2. ICU stay was shorter in groups 1 and 2—2.3±0.9 days vs. 3.5±1.1 days for group 3, P=0.004. All patients received dopamin postoperatively, however in a lower dose in groups 1 and 2, 4.5 vs. 13.5 μg/kg/min. Dobutamine was added in 23% of the patients (group 1), 32% (group 2) and 95% (group 3). Adrenalin/amrinonum was required in 40% of the patients in group 3, 5% in group 2 and none in group 1. Group 1 patients had a better improvement of cardiac performance than group 2, while other parameters did not differ. Three months follow up of hospital survivors showed no group differences. Conclusions: The use of preoperative IABP in high risk patients lowers hospital mortality and shortens the stay in ICU, due to improved cardiac performance, compared to a controls. The procedure was cost-beneficial. One day preoperative IABP treatment improves cardiac performance more than 1–2 h preoperative IABP treatment, but does not significantly affect the outcome in terms of hospital mortality or postoperative morbidity.     

Early and long term outcome of the arterial switch operation for transposition of the great arteries: predictors and functional evaluation

Objectives: The aims of this report were to study the early and late outcome in terms of mortality, freedom from reoperation, predictors for late pulmonary stenosis (PAS) and insufficiency of the neo-aortic valve (AVI) in patients with transposition of the great arteries (TGA) undergoing arterial switch operation (ASO). Materials and methods: Between January 1990 and December 2001, 134 patients with TGA underwent ASO. The patients were divided in Group I (n=88)-TGA with intact ventricular septum and Group II (n=46)-TGA with ventricular septal defect (VSD). The pulmonary artery was reconstructed employing the direct anastomosis technique (PT-I) in 21 (15.7%) patients, the double-patch technique (PT-II) in 41 (30.6%), single pantaloon patch (partial circumference) (PT-III) in 46 (34%) and single pantaloon patch (total circumference) (PT-IV) in 35 (26%) patients. The mean follow-up was 3.4±1.3 years. Results: The hospital mortality was 17 (12.7%) patients. The mortality in Group I was significantly lower than Group II (P=0.002). The overall actuarial survival at 1, 3 and 5 years follow-up resulted to be 98, 93, and 91.5%, resulting to be significantly higher in Group I (P=0.032). The multivariate analysis revealed the complex TGA (P=0.007), VSD (P=0.032), coronary anomalies (P=0.004), aortic coarctation or hypoplastic aortic arch (P=0.021), left ventricular outflow tract obstruction (LVOTO) or moderate PAS (P=0.041) as strong predictors for poor free-reoperation cumulative survival. A strong inverse correlation was found between the mean trans-pulmonary gradient at follow-up and the age at the operation (r=−0.41, P<0.0001). The univariate analysis revealed the PT-I technique (P=0.002), prior moderate PAS (P=0.0001), and age <1 month (P=0.018) as strong predictors for moderate-to-severe PAS. The neo-AVI incidence was significantly higher in Group II (P=0.011). Predictors for neo-AVI were male sex (P=0.003), preoperative neo-AV Z-score >1 (P<0.001), prior or concomitant operation for aortic coarctation or hypoplastic aortic arch (P=0.001), LV retraining (P=0.003). Conclusion: ASO remains the procedure of choice for the treatment of various forms of TGA with acceptable early and later outcome in terms of overall survival and free reoperation. Strong predictors for poor overall free-reoperation survival are complex TGA, VSD, coronary anomalies, aortic coarctation and LVOTO or moderate PAS. The pulmonary artery reconstruction using a single ‘pantaloon patch’ seems to offer less residual stenosis. Patients with a VSD and a significant mismatch between the neo-aortic root and distal aorta are at a higher risk for developing postoperative neo-AVI.