Cardiac function during exercise in patients with coronary bypass surgery assessed by continuous ventricular function monitoring

The response of left ventricular function during exercise and recovery after exercise was assessed in 52 patients with coronary artery bypass surgery by means of a radionuclide continuous ventricular function monitor. This system consists of 2 radionuclide detectors, recorder and a computer. After the equilibration of 20 mCi technetium 99m-labeled autologaous red blood cells into the intravascular space, the beat by beat radionuclide data were summed for 20-sec intervals to measure left ventricular ejection fraction (EF). Before surgery, the mean EF decreased with exercise from 51 +/- 9% to 45 +/- 11% (p less than 0.001). Cardiac response was divided into 4 types according to the profiles of the EFs during exercise. In 6 patients, EF continued to increase until maximal exercise (type A). In 10 patients, EF initially increased and then decreased in late exercise stages (type B). In 9 patients, EF did not change significantly during exercise (type C). In 27 patients, EF decreased throughout exercise (type D). After surgery, the mean EF increased with exercise from 53 +/- 10% to 60 +/- 13% (p less than 0.001). Thirty-five patients showed type A, 9 type B, 5 type C, and 3 type D. Two type D and 5 type B patients had occluded grafts or ungrafted coronary arteries. Four patients with complete revascularization including an internal thoracic artery and saphenous vein grafts showed type B. Three patients with extensive infarction and poor left ventricular function showed type C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessment of left ventricular function during off-pump coronary artery bypass surgery.

Left ventricular function is commonly impaired following cardiopulmonary bypass and cardioplegic arrest. Off-pump coronary artery bypass surgery (OPCABG) offers promise of better myocardial protection, although the effect of multiple regional ischemic events on global myocardial function is unknown. Twenty-eight patients undergoing multivessel OPCABG were assessed with transesophageal echocardiography and pulmonary artery catheterization prior to and following revascularization. Both load-dependent and relatively load-independent measurements of systolic and diastolic performance were measured. Mean +/- SD age was 62+/-8.3 years, grafts performed were 3.8+/-1.6, and 28% of patients had fractional area change (FAC) <50%. Blood pressure was lower following OPCABG associated with a fall in systemic vascular resistance. There was no difference in measurements of systolic functional FAC, cardiac index, or afterload-corrected FAC. Diastolic function appeared to improve based on mitral inflow and pulmonary vein Doppler measurements, but this occurred at a significantly lower pulmonary capillary wedge pressure and end-diastolic area. No change in diastolic function was found using less load sensitive indices of diastolic function (color M-mode Doppler, tissue Doppler and instantaneous end-diastolic stiffness). Left ventricular systolic and diastolic function is preserved following multivessel OPCABG.     

Exercise response assessed by continuous monitoring of ventricular function in patients with coronary bypass operations.

The response of left ventricular function during exercise and recovery after exercise was assessed in 35 patients with coronary artery bypass grafting before and after the operation by means of a continuous ventricular function monitor, which records serial beat-to-beat radionuclide data and calculates left ventricular ejection fractions every 20 seconds. The mean ejection fraction decreased with graded bicycle exercise from 48% +/- 9% to 41% +/- 11% (p less than 0.001) before operation but increased with exercise from 50% +/- 9% to 55% +/- 11% (p less than 0.001) after operation. Cardiac response was divided into four types with respect to the profiles of the ejection fractions during exercise. Type A continued to increase; type B initially increased but then decreased in late exercise stages; type C did not change significantly; type D continued to decrease. Most patients had type C or D responses before operation but type A after operation. Seven patients with occluded grafts or ungrafted coronary arteries had type B or D responses. Three patients with complete revascularization, including an internal thoracic artery and saphenous vein grafts, had type B responses. Three patients with extensive infarction and poor left ventricular function showed type C. In the early recovery period after exercise, most patients had an "overshoot" elevation of ejection fraction. The mean value increased from 59% +/- 10% before operation to 64% +/- 11% after operation (p less than 0.01). The recovery time after exercise was reduced from 2.8 minutes before operation to 1.8 minutes after operation (p less than 0.001). The continuous ventricular function monitor elucidated changes in left ventricular function both during exercise and recovery after exercise, as well as unmasking abnormalities in left ventricular function after coronary bypass operation.     

Assessment of left ventricular function following coronary bypass surgery: a non-invasive study

Hardarson, T., Ziady, G. M., and Khattri, H. N. (1974).Thorax, 29, 359-365. Assessment of left ventricular function following coronary bypass surgery: a non-invasive study. In a series of 15 patients with ischaemic heart disease, systolic time intervals (STI) were measured before, and at one week, three months, and six months following coronary vein-graft surgery. Preoperatively, the left ventricular ejection time (LVET) was abnormally short in seven patients, while the pre-ejection period was abnormally long in seven patients, suggesting impaired left ventricular function. At one week after surgery LVET and total electromechanical systole (QA2) were significantly abbreviated. This may be explained by the transient fall in cardiac output or postoperative neurohumoral changes. For the group as a whole, no significant changes were found at three or six months, suggesting that cardiac function was generally preserved rather than improved. However, in individual patients changes in STI correlated with the clinical and angiographic estimate of success of the operative treatment.     

Evaluation of left ventricular function in coronary bypass surgery

OBJECTIVES: To evaluate non-invasive indexes measuring systolic and diastolic ventricular function. Eleven coronary artery bypass grafting (CABG) patients were investigated in order to assess the ability of preoperative ejection fraction (EF) and end diastolic pressure (EDP) to predict left ventricular function determined non-invasively at surgery. DESIGN: End-systolic elastance (Ees) was assessed perioperatively using transoesophageal echocardiographic area estimation and arterial pressure monitoring during preload variations (caval balloon). Diastolic function was evaluated using three different echo/Doppler indexes. RESULTS: EF correlated positively to Ees (r = 0.69, p = 0.03). No correlations were found between EDP and the perioperative diastolic indexes. Ees fell from pre-bypass to post-bypass (from 9.0 +/- 2.7 to 4.7 +/- 1.7 mmHg/cm2, mean +/- SD, p < 0.001), but no alterations in diastolic parameters occurred. CONCLUSIONS: A positive correlation was found between preoperative EF and Ees at surgery. The semi-invasive Ees detected a systolic "stunning" after cardiopulmonary bypass and is promising as a surveillance tool for left ventricular perioperative function and treatment. No correlations between preoperative EDP and non-invasive diastolic indexes were found, and assessment of perioperative diastolic function needs further refinement.     

Right ventricular function after coronary surgery with or without bypass

BACKGROUND AND OBJECTIVE: Myocardial protection during aortic clamp period may sometimes be inadequate, especially for the right. The aim of this study was to compare right ventricle function after cardiac surgery with or without bypass. METHODS: Patients undergoing multivessel coronary surgery with proximal severe right coronary lesion were included in a prospective observational cohort study including 29 patients undergoing coronary surgery with or without bypass. All patients were monitored with a pulmonary artery catheter with continuous right ventricular function. Right ventricular ejection fraction was measured at the arrival in ICU, 1, 3, 6, and 18 hours later. RESULTS: The number of grafts that was higher in the bypass group (4.0 +/- 1.3) than in the off-pump group (2.6 +/- 0.6, p = 0.001). In the on-pump group, the right ventricular ejection fraction significantly decreased from 32.9 +/- 2.8 at arrival in ICU to 26.1 +/- 2.4, 6 hours later whereas in the off-pump group, it did not significantly change (32.4 +/- 1.8 to 31.9 +/- 2.3). Meanwhile, at the same time intervals, CVP was significantly lower in the off-pump group. CONCLUSIONS: In patients with severe right coronary stenosis, off-pump cardiac surgery seemed to provide better right ventricular protection.     

Electromechanical left ventricular resynchronisation by coronary artery bypass surgery.

OBJECTIVE: In patients with coronary artery disease (CAD), the normal electromechanical response to dobutamine stress is deranged: QRS duration lengthens rather than shortens, left ventricular asynchrony develops, post-ejection shortening appears, and total isovolumic time (the time in the cardiac cycle when the ventricle is neither ejecting nor filling) increases rather than falls, all of which blunt the normal rise in cardiac output. We aimed to study the effect of revascularisation on these stress-induced electromechanical abnormalities and their effect on peak cardiac output after coronary artery bypass grafting (CABG). METHOD: 20 unselected patients were studied before and after CABG. Long axis asynchrony was determined by (i) delay in the onset of shortening, (ii) amplitude and (iii) duration of post-ejection shortening. Total isovolumic time (in s/min), calculated as [60-(total ejection time+total filling time)] and cardiac output were measured by Doppler echocardiography. RESULTS: Before CABG: QRS duration broadened with stress (by 7+/-8 ms, P<0.01) and post-ejection shortening increased (amplitude by 1.1+/-0.7 mm, P<0.01, duration by 8+/-9 ms, P<0.01). Total isovolumic time increased (by 3+/-3 s/min, P<0.01) and cardiac output rose (by 2.8+/-1.2 l/min, P<0.01). After CABG: QRS duration shortened with stress (by 5+/-4 ms, P<0.01) post-ejection shortening decreased (amplitude and duration fell by 0.4+/-0.5 mm and 22+/-14 ms, respectively), total isovolumic time shortened (by 3+/-3 s/min) and cardiac output increased (by 5.1+/-1.8 l/min, all P<0.01). Changes in total isovolumic time and duration of post-ejection shortening with stress were independent predictors of the increase in peak cardiac output after revascularisation (total R(2)=0.69). Independent predictors of changes in total isovolumic time with stress were those in QRS duration and the duration of post-ejection shortening (total R(2)=0.75). In turn, changes in the duration of post-ejection shortening were closely associated with alterations in the delay in long axis shortening (r(2)=0.50) which correlated with changes in QRS duration (r(2)=0.59, all P<0.001). CONCLUSIONS: Revascularisation resynchronises left ventricular wall motion by restoring the normal activation response to stress, thereby reducing total isovolumic time and normalising peak cardiac output response to stress.     

Isoflurane-fentanyl anesthesia for coronary bypass surgery in patients with good left ventricular function

The hemodynamic effects of a balanced anesthetic technique where a moderate dose of fentanyl (32 micrograms/kg) is supplemented with isoflurane were studied in 15 patients with good left ventricular function. Mean inspired isoflurane concentration was 0.63% during induction and 0.74% during maintenance. Induction of anesthesia was associated with a significant decrease (p less than 0.05) in systolic and diastolic pressure and left ventricular stroke work index (LVSWI). During maintenance systolic blood pressure and LVSWI remained significantly depressed. It is concluded that isoflurane-fentanyl anesthesia has myocardial depressant properties. There is a reduced incidence of break-through hypertension during noxious stimuli, when compared with high-dose fentanyl anesthesia. During maintenance, clinical signs that could reflect myocardial ischemia were not observed. Heart enzymes remained within normal range postoperatively in all patients and ECG morphology was unchanged.     

Change in right ventricular function during off-pump coronary artery bypass graft surgery.

OBJECTIVES: Hemodynamic derangement during displacement of beating heart in off-pump coronary artery bypass graft (OPCAB) surgery might be related with right ventricular (RV) dysfunction. We evaluated RV function and hemodynamic alterations using a thermodilution pulmonary artery catheter. METHODS: The study included 30 patients undergoing OPCAB, using single pericardial suture and tissue stabilizer. A thermodilution pulmonary artery catheter for continuous monitoring of the cardiac output (CO), right ventricular ejection fraction (RVEF) and RV volume was inserted before anesthesia. The hemodynamic variables were measured after the induction of anesthesia, 5 min after the heart was positioned for each coronary anastomosis and after the sternum was closed. RESULTS: There was no significant change in the RVEF and cardiac index during anastomosis of the left anterior descending artery and right coronary artery. However, the significantly reduced RVEF accompanied by an increase in RV afterload and decrease in the CO was observed during anastomosis of the obtuse marginal (OM) artery. RV volumes did not significantly change during anastomoses, though the right atrial pressure increased during anastomoses of all coronary arteries. CONCLUSIONS: The displacement of beating heart for positioning during anastomosis of the graft to OM artery caused significant derangement of RV function and decrease in CO. A thermodilution catheter continuously measuring the CO and RVEF was useful to monitor the change in RV function and volume during OPCAB.     

Assessment of coronary artery bypass surgery by exercise thallium imaging.

The purpose of this study was to assess the coronary artery bypass grafting (CABG) in exercise thallium-201 scintigraphy. The study was performed on 18 consecutive patients undergoing elective surgery. We compared the results of the scintigraphic examinations, 1 week before and 1 month postoperatively. Of the 47 bypass grafts, 20 (42. 6%) grafts contributed to the improvement of the ischemic areas and 38% of the bypass grafts did not change the scintigraphic patterns after surgery. Some bypass grafts had been performed on the stenotic arteries that dominated the areas which preoperatively showed normal exercise scintigraphic patterns yet were considered to worsen in the near future. Such grafts main contribution may be to protect and to increase the overall myocardial washout ratio for prevention of an enlargement of ischemic areas.     

Left ventricular function after aortocoronary bypass surgery.

Aortocoronary bypass operations without additional myocardial surgery or valve replacement were performed at Ullev?l Hospital in 190 patients during the period May 1971 to Dec. 1975. Postoperatively re-examination was made by left-heart catheterization in 124 patients at a mean interval of 18.2 months and right-heart catheterization in 108 patients at a mean interval of 16.0 months after surgery. The mean postoperative values for PCVP at rest, PCVP during exercise, LVEDP before contrast and LVEDP after contrast were significantly lower than the mean pre-operative values. The difference between pre- and postoperative values were largest in patients with elevated PCVP or LVEDP values before surgery, whereas in patients with low pre-operative values the mean values after surgery were unchanged or increased. The results indicate that marked improvement of left ventricular function may occur after aortocoronary bypass operations, even in patients with signs of ventricular failure at rest. A stress test is, however, of importance in evaluating the haemodynamic consequences of coronary surgery. No difference was found in patients with single versus patients with double or triple shunts. Post-operative shunt occlusion was found in 44 of 258 grafts at re-examination. No difference was found between patients with all shunts patent and patients with one or more shunts occluded as regard to mean postoperative PCVP and LVEDP values.     

Improvement in resting ventricular performance following coronary bypass surgery

To assess the changes in resting left ventricular (LV) function following coronary bypass surgery, technetium 99m-labeled multiple equilibrated blood pool gated scans were performed in 53 consecutive patients at rest, before operation, and at 24 hours and 1 week after operation. Left ventricular ejection fraction (LVEF) and end-diastolic volume (EDV) were measured. The LVEF increased significantly from a preoperative value of 49 +/- 2% to 56 +/- 2% at 24 hours after operation (p less than 0.05) and 56 +/- 2% at 1 week following operation (p less than 0.05 compared with the preoperative value). The EDV also exhibited significant changes, decreasing from a preoperative value of 148 +/- 8 ml to 91 +/- 11 ml at 24 hours (p less than 0.001) and 114 +/- 9 ml at 1 week (p less than 0.01 compared with the preoperative value). When the patients were divided into two groups according to the preoperative LVEF (Group 1, LVEF of greater than or equal to 50%; Group 2, LVEF of less than 50%), the observed changes were similar. This study demonstrates significant improvement in resting LV function 24 hours following coronary bypass surgery. This improvement persists at 1 week and is not related to the degree of preoperative impairment. We conclude that the combination of successful revascularization and optimal myocardial protection can result in significant improvement of LV function at rest.