Influence of intra-aortic balloon pumping on cerebral blood flow pattern in patients after cardiac surgery

BACKGROUND AND OBJECTIVE: The effects of intra-aortic balloon pumping (IABP) on cerebral perfusion are still a matter of debate. End-diastolic reversal of blood flow in cerebral arteries has been observed in a small number of patients. We prospectively investigated the incidence and the amount of transient cerebral artery blood flow reversal during balloon pumping in patients recovering from cardiac surgery. METHODS: In 23 patients receiving IABP support, blood flow velocities in the right middle cerebral artery were assessed by transcranial Doppler-sonography. Additionally, systemic haemodynamics were monitored. In each patient, measurements were performed at three different pump settings: without support, assist ratio 1 : 1 and assist ratio 1 : 2. RESULTS: In 8 of 23 patients, balloon pumping caused a transient diastolic reversal of blood flow in the middle cerebral artery during balloon deflation. Antegrade mean flow velocity in the middle cerebral artery significantly increased from 57 +/- 27 to 61 +/- 26 (assist ratio 1 : 1) and 61 +/- 29 cm s(-1) (assist ratio 1 : 2) (P < 0.05). Taking transient blood flow reversal into account, net mean flow velocity did not increase with balloon pump support. Systemic haemodynamic parameters remained unchanged. CONCLUSION: Left ventricular support with IABP significantly changed flow patterns in basal cerebral arteries of our patients. In 35% of patients, support resulted in a transient reversal of intracranial blood flow which counterbalanced a slight increase in mean antegrade flow.     

Transfemoral balloon aortic occlusion during open cardiopulmonary resuscitation improves myocardial and cerebral blood flow

These experiments were designed to determine whether the limited cardiac output during open cardiac massage could be preferentially directed to the coronary and cerebral vessels by balloon occlusion of the descending thoracic aorta. Sixteen dogs were instrumented to monitor cardiac output and left atrial, right atrial, right ventricular, left ventricular, and arterial blood pressures. Measurements of myocardial and cerebral blood flow distribution during massage were made using the radioactive microsphere technique. Each animal underwent two episodes of fibrillation and resuscitation. In one episode the arrest was managed by open massage alone, and in the other, open massage was accompanied by balloon occlusion, with the order randomized. When compared to control, open cardiac massage was associated with a significant decrease in mean arterial pressure; however, the addition of balloon occlusion produced a 130% increase in the mean arterial pressure that was obtained during open CPR (control, 93 +/- 5 mm Hg; massage alone, 35 +/- 2 mm Hg; massage + balloon, 76 +/- 2 mm Hg, P less than 0.01). In a similar fashion, although the absolute blood flow was reduced by 50% when compared to control, the blood flow (ml/min/g) to the brain and heart during massage was 100% better when balloon occlusion was employed (brain: control, 0.41 +/- 0.03; massage only, 0.05 +/- 0.01; massage + balloon, 0.25 +/- 0.02, P less than 0.01; heart: control, 1.46 +/- 0.11; massage alone, 0.35 +/- 0.05; massage + balloon, 0.71 +/- 0.05, P less than 0.01). These results suggest that aortic occlusion significantly increased myocardial and cerebral perfusion patterns during ventricular fibrillation and open cardiac massage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Combined Impella and intra-aortic balloon pump support to improve both ventricular unloading and coronary blood flow for myocardial recovery: an experimental study

Abstract:  Some patients in need of hemodynamic support do not respond to intra-aortic balloon pump (IABP) therapy. Hemodynamic stability can then be obtained by a more potent cardiac assist device, like the Impella catheter pump. Whether additional IABP support additional to Impella support can provide more optimal hemodynamic myocardial conditions is examined in this study. Seven sheep were implemented with IABP and Impella. An acute myocardial infarction was induced. Hemodynamic performance was assessed during baseline, during Impella support and IABP support individually, and during the combined Impella plus IABP support. The Impella support provided a reduction of afterload with 30% and an increase of coronary artery flow with 47%. The IABP increased coronary artery flow (13%), carotid artery flow (16%), and aortic ascending blood pressure (6%); a similar (but stronger) effect was provided when using the IABP support additional to Impella support and, respectively, increases of 33, 21, and 19% were established. The oxygen demand–supply ratio decreased by 25% due to the extra use of the IABP. A combination of IABP and Impella provides the most optimal hemodynamic myocardial conditions compared to either stand-alone support.     

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.     

The way the intra-aortic balloon catheter moves within the aorta as a possible mechanism of balloon associated morbidity

This study set off to investigate which mode of weaning of an intra-aortic balloon pump (IABP) produces more aortic trauma. With the use of a perfusion pump, an intact porcine aorta with an IABP in situ, was studied. Angioscopic images of the interior of the aorta were obtained. Whilst keeping steady blood pressure and flow, an 'aortic impact score' was calculated. Endoscopically there is a 'whipping' effect of the balloon shaft on the lateral aortic wall, which appears to be prominent in 1:3 mode. The aortic impact score at 0.5, 6 and 12 h during the experiments was: (1) When weaning by mode: a) 1:1 3.3+/-0.6, 4.0+/-1.0 and 4.3+/-0.6; b) 1:2 4.7+/-0.6, 6.7+/-0.6 and 7.0+/-0.0; c) 1:3 8.7+/-0.6, 11+/-1.0 and 11.7+/-0.6. (2) Weaning by augmentation: a) 75% 2.3+/-0.6, 2.7+/-0.6 and 3.0+/-0.0; b) 50% 1.3+/-0.6, 1.3+/-0.6 and 1.7+/-0.6. An increasing score was observed while weaning by mode (P<0.05). The 1:3 mode produces marked intimal disruption that worsens with time.     

Experience in 100 transthoracic balloon pumps.

We retrospectively reviewed our last 100 consecutive patients who had an intraaortic balloon pump (IABP) placed through the ascending aorta for postoperative cardiogenic shock. Eighty-one patients survived to have their IABP removed and were evaluated for complications. Complications that may have been related to the transthoracic route of IABP introduction included balloon rupture in 6.2% (5/81), cerebral vascular accident in 2.5% (2/81), transient ischemic attack in 1.2% (1/81), bleeding at the IABP arteriotomy site in 3.7% (3/81), and mediastinitis in 3.7% (3/81). Compared with expected rates of development of complications in this high-risk group of patients, it appeared that balloon rupture and mediastinal bleeding were increased because of the transthoracic placement of the IABP. The rates of neurologic events and mediastinal infection do not appear to be increased. Transthoracic IABP placement avoids ischemic problems in the lower extremities and has proved a useful route for IABP introduction.     

Enhanced intra-aortic balloon pump: markedly improved systemic hemodynamics and cardiac function in canines with severe,acute left ventricular failure

Intra-aortic balloon pumps (IABPs) cannot sustain hemodynamics if the left heart is severely injured. An enhanced IABP was evaluated in 6 anesthetized dogs with acute stenosis of the left anterior descending coronary artery, regional left ventricular (LV) stunning, and global LV dysfunction. An IABP balloon was inserted into the descending aorta and an external chamber containing another IABP balloon was connected to the aorta through a catheter inserted into the left subclavian artery. This emulated the enhanced IABP with a conduit from its external chamber passing axially through an internal IABP balloon. Compared to IABP, enhanced IABP improved hemodynamics and LV function in all conditions. During severe LV dysfunction and circulatory failure, IABP failed to augment diastolic aortic pressure or improve coronary and carotid flows. Enhanced IABP augmented diastolic pressure from 32 +/- 3 mm Hg to 87 +/- 2 mm Hg and increased coronary and carotid flows. Enhanced IABP may be a lifesaving device for patients with severe LV failure.     

Single-stage repair of aortic coarctation with ventricular septal defect using isolated cerebral and myocardial perfusion.

OBJECTIVE: To avoid hypothermic circulatory arrest, we have repaired aortic coarctation with ventricular septal defect (VSD) in a one-stage procedure using an isolated cerebral and myocardial perfusion technique, and retrospectively compared this novel approach to the conventional two-stage approach. METHODS: Between October 1991 and February 1999, 24 infants, aged 4-137 days (median, 27 days) and weighing 1.7-4.3 kg (median, 3.0 kg), underwent the repair of aortic coarctation with VSD either in one (group I, n=11) or two stages (group II, n=13). In Group I, an arterial cannula for cardiopulmonary bypass was inserted into the ascending aorta in six patients with coarctation only, or into a polytetrafluoroethylene (PTFE) graft which was anastomosed to the innominate artery in the remaining five who had hypoplastic arches. A cross-clamp was placed between the innominate and left carotid arteries. The bypass flow was reduced to 30-50% of full flow at 28 degrees C, thereby maintaining a radial artery pressure of 30-45 mmHg. At this point, the aortic coarctation was repaired by an end-to-end arch anastomosis, while maintaining brain perfusion and with the heart still beating. In five patients with hypoplastic aortic arches, the innominate artery proximal to the graft was then secured down and the arch anastomosis was extended to the distal ascending aorta, while providing isolated cerebral perfusion and cardioplegic arrest. After arch reconstruction was performed, the clamp was moved onto the ascending aorta, and the VSD was closed with systemic perfusion. In contrast, for group II patients, coarctation repairs were performed through a posterolateral approach, and existing VSDs were closed as secondary procedures. RESULTS: The mean isolated cerebral and myocardial perfusion time for group I was 13 min (range, 7-20 min). The myocardial ischemic time did not differ between groups I and II (43+/-4 vs. 42+/-5 min, not significant). There were no hospital mortalities or neurological complications in either group, but one late death in each group. CONCLUSION: Single-stage repair of aortic coarctation with VSD does not increase myocardial ischemic time compared to the traditional two-stage approach. The isolated cerebral and myocardial perfusion technique may offer substantial brain and myocardial protection during aortic arch reconstruction.     

Determination of cerebral blood flow dynamics during retrograde cerebral perfusion using power M-mode transcranial Doppler

BACKGROUND: Retrograde cerebral perfusion (RCP) during profound hypothermic circulatory arrest has been used as an adjunct for cerebral protection for repairs of the ascending and transverse aortic arch. Transcranial Doppler ultrasound has been used to monitor cerebral blood flow during RCP with varying success. The purpose of this study was to characterize cerebral blood flow dynamics during RCP using a new mode of monitoring known as transcranial power motion-mode (M-mode) Doppler ultrasound. METHODS: Data on pump-flow characteristics and patient outcomes were collected prospectively for patients undergoing ascending and transverse aortic arch repair. Retrograde cerebral perfusion during profound hypothermic circulatory arrest was used for all operations. Intraoperative cerebral blood flow dynamics were monitored and recorded using transcranial power M-mode Doppler ultrasound. RESULTS: Between August 2001 and March 2002, we used transcranial power M-mode Doppler ultrasound monitoring for 40 ascending and transverse aortic arch repairs during RCP. Mean RCP time was 32.2 +/- 13.8 minutes. Mean RCP pump flow and RCP peak pressure for identification of cerebral blood flow were 0.66 +/- 0.11 L/min and 31.8 +/- 9.7 mm Hg, respectively. Retrograde cerebral blood flow during RCP was detected in 97.5% of cases (39 of 40 patients) with a mean transcranial power M-mode Doppler ultrasound flow velocity of 15.5 +/- 12.3 cm/s. In the study group, 30-day mortality was 10.0% (4 of 40 patients). The incidence of stroke was 7.6% (3 of 40 patients); the incidence of temporary neurologic deficit was 35.0% (14 of 40 patients). CONCLUSIONS: Transcranial power M-mode Doppler ultrasound consistently demonstrated retrograde middle cerebral artery blood flow during RCP. Transcranial power M-mode Doppler ultrasound can provide optimal RCP with individualized settings of pump flow.     

Efficacy of intravascular volume resuscitation in dogs with acute cardiac tamponade

Whether cardiac tamponade causes myocardial ischemia and whether volume resuscitation can improve coronary perfusion pressure and myocardial blood flow were studied by hemodynamic responses to three blood infusions of 15 ml/kg in dogs with left ventricular hypovolemia produced by cardiac tamponade (N = 10) or hemorrhage (N = 10). Coronary perfusion pressure decreased to 37 +/- 2 mm Hg with tamponade and 39 +/- 1 mm Hg with hemorrhage, causing significant blood flow decreases in both ventricles. Myocardial oxygen extraction increased significantly in both groups without affecting lactate extraction. Volume resuscitation after hemorrhage progressively restored hemodynamic variables to baseline values. Volume resuscitation after tamponade did not increase stroke volume, whereas it increased coronary sinus pressure to 19.2 +/- 1.0 mm Hg (p less than 0.05). Coronary perfusion pressure increased to 53 +/- 5 mm Hg following the first infusion (p less than 0.05), but exhibited no further improvement. Tamponade did not produce myocardial ischemia. Coronary perfusion pressure and blood flow were not restored to baseline values with volume resuscitation since coronary sinus pressure rose incrementally with each volume infusion.     

New aspects on the role of blood pressure and arterial stiffness in mechanical assistance by intra-aortic balloon pump: in-vitro data and their application in clinical practice

Despite the well-known beneficial effects of the intra-aortic balloon pump (IABP) generally, there are still some clinical conditions accompanied by IABP ineffectiveness. The aim of this study was the investigation of the independent effects of arterial stiffness and blood pressure on acute IABP effectiveness. For this purpose, a mock circulatory system and 20 patients with cardiogenic shock due to acute myocardial infarction, were employed. It was shown that IABP acute efficiency was determined primarily by arterial compliance (AC) rather than blood pressure alone. IABP induced low hemodynamic effects in patients with systolic blood pressure > 80 mm Hg but with increased AC, whereas IABP resulted in greater hemodynamic effectiveness in cases with systolic pressure < 70 mm Hg but lower AC. The present study provides evidence concerning the hemodynamic conditions, which might lead to optimization of IABP or to the prediction of its acute hemodynamic performance, based on both measurements of AC and blood pressure.     

The acute effect of intra-aortic balloon counterpulsation during extracorporeal life support: an experimental study

Hemodynamically unstable patients supported by an extracorporeal life support (ECLS) circuit often receive additional support by intra-aortic balloon pump (IABP). However, it is not established whether support of the failing heart is improved by adjunctive IABP in both peripheral cannulation (PC) and central cannulation (CC) settings. Seven sheep were supported by an IABP and an ECLS system which were cannulated centrally as well as peripherally. In each cannulation configuration, hemodynamic and cardiac function indices were measured at baseline, ECLS, and ECLS plus IABP. The primary variables were mean coronary artery flow (Qcor), diastolic pressure time index (DPTI), left ventricular (LV) pressure-volume area (PVA), and tension time index (TTI). Additional IABP with ECLS support (CC/PC) decreased LV afterload (LV systolic peak pressure -4%, P<0.05/-8%, P<0.02), as well as TTI -2%/-10% and PVA -10%/-12% (P<0.03). Coronary perfusion was increased by additional IABP: CC, Qcor, +9%, and DPTI, +18% (P<0.02); PC, Qcor,+6%, and DPTI, +11% (P<0.05). IABP augmented the myocardial oxygen supply/demand ratios (CC/PC): Qcor/(PVA.heart rate) (+21%/+22%, P<0.02) and DPTI/TTI (+27%/+24%, P<0.03). In case of low arterial pressure (<50 mm Hg) and reduced ECLS flow, the overall hemodynamic profile improved only with central cannulation. We conclude that in both central and peripheral ECLS cannulation settings, adjunctive IABP improves the myocardial oxygen supply demand balance. In case of low cardiac output and insufficient extracorporeal flow with PC, adjunctive IABP may be contraindicated.     

The possibility of a veno-arterial bypass system using the Abiomed BVS 5000

Effect of Abiomed BVS 5000 (Cardiovascular Inc., Danvers, MA, U.S.A) has been reported for mechanical assist circulation in cardiogenic shock. However, this pump is generally used as a ventricular assist device, not as a device for veno-arterial bypass. Therefore, we evaluated its effectiveness through an experiment. The left anterior descending branch of pigs' heart was ligated to prepare a model of acute myocardial infarction, and after the onset of cardiogenic shock, circulation was initially supported for 30 min using the BVS 5000, followed by support for another 30 min using a Gyro pump (Gyro, Kyocera, Inc., Kyoto, Japan). Subsequently, circulation was additionally supported for 30 min using both a Gyro and an intra-aortic balloon pump (IABP) (Tokai Medical Inc., Aichi, Japan) (Gyro + IABP). Circulation was supported in each group at 30-min intervals in the reversed order of assisted circulation. Although the mean aortic pressure, pump flow, and total flow were not significantly different among the three setups, the pulse pressure was 48.2 +/- 3.3, 12.2 +/- 2.2, and 29.9 +/- 3.8 mm Hg in Abiomed, Gyro, and Gyro + IABP, respectively. Although neither coronary arterial nor myocardial blood flow showed significant differences among the three setups, the renal arterial blood flow was significantly larger in BVS 5000 compared to the other two setups. In this study, we selected an alpha-cube (Platium Cube NCVC 6000, Edwards Research Medical Inc., Salt Lake City, UT, U.S.A.), which is considered as an oxygenator that produces minimum pressure loss. Therefore, the pulsatile flow we obtained with the Abiomed was maintained even after we started using the oxygenator. The pulsatile flow had positive effects on renal circulation and peripheral circulation.     

The intra-aortic cannula pump: A novel assist device for the acutely failing heart.

OBJECTIVE: The intra-aortic cannula pump is a catheter pump designed to support the acutely failing heart. It expels blood from the left ventricle into the ascending aorta in a pulsatile flow pattern. The aim of the study was to analyze the hemodynamic performance of this new intracardiac support system in acute heart failure. METHODS: A 24F cannula was studied in a series of 16 sheep. Hemodynamic changes were assessed in the nonfailing, the moderately failing, and the severely failing heart. Heart failure was induced by an injection of microspheres into the left anterior descending coronary artery. The cannula was inserted through the aortic arch and introduced through the aortic valve into the left ventricle. RESULTS: Cannula insertion was feasible in all animals. Flow through the intra-aortic cannula flow was increased to a maximum of 3 L/min. No hemodynamic changes were observed in the nonfailing heart. A significant increase in cardiac output was observed in the moderately and severely reduced left ventricle (2.67 +/- 0.7 L to 3.51 +/- 0.83 L; P =.001; and 1.18 +/- 0.77 L to 2.43 +/- 0.44 L; P =.001, respectively). A drop in left atrial pressure was achieved in moderate and severe heart failure (14.1 +/- 5.93 mm Hg to 9.71 +/- 2.63 mm Hg; P =.0001; and 23 +/- 7.16 mm Hg to 11.2 +/- 2.55 mm Hg; P = 0.0001, respectively). Systolic and diastolic systemic blood pressures increased in the severely failing heart (57.3 +/- 12.8 mm Hg to 75.4 +/- 11.2 mm Hg; P =.0001; and 35.6 +/- 8.2 mm Hg to 60 +/- 14.3 mm Hg; P =.0006, respectively). CONCLUSIONS: Hemodynamic data demonstrate the beneficial effects of the intra-aortic cannula pump in moderate and severe heart failure. The intra-aortic cannula pump represents a new modality for the treatment of acute heart failure.     

Acute experimental study of Abiomed BVS5000 as a V-A bypass to cardiogenic shock models.

PURPOSE: Abiomed BVS5000 is generally used as a ventricular assist device, and there have been no reports of its application to a veno-arterial bypass (V-A bypass). In the present study, we developed a new V-A bypass system using this pump and examined its usefulness experimentally. MATERIALS AND METHODS: Pigs (n=21; 37.4+/-2.2 kg) with cardiogenic shock were divided into the following three groups: (1) Abiomed group (Abiomed BVS5000); (2) nonpulsatile pump (NP)+intra-aortic balloon pump (IABP) group (centrifugal pump and IABP); and (3) NP group. In all three groups, assisted circulation using the pumps was performed for 3 h after the shock. Hemodynamic data and blood specimens were measured before and immediately after the shock, and again at 1, 2, and 3 h after. The individual variations were reduced by evaluation of the measured value/preshock value ratio, not by evaluation of the absolute values. RESULTS: The coronary arterial blood flows at 3 h after the shock were significantly larger in the Abiomed and NP+IABP groups than in the NP group (1.32+/-0.34 and 1.24+/-0.05 vs. 1.05+/-0.11, P<0.05), and the renal arterial and renal cortical tissue blood flows were significantly larger in the Abiomed group than in the NP+IABP and NP groups (renal artery: 1.30+/-0.17 vs. 0.89+/-0.20 and 0.68+/-0.10, P<0.05; renal cortical tissue: 0.74+/-0.25 vs. 0.62+/-0.05 and 0.43+/-0.18, P<0.05). The lactate/pyruvate ratios were significantly lower in the Abiomed groups than in the NP group (25.2+/-1.6 vs. 36.0+/-3.1, P<0.05). CONCLUSION: The results suggest that a V-A bypass using an Abiomed BVS5000 is a useful treatment for organ blood flow redistribution after shock.     

Preoperative intra-aortic balloon support in surgery for left main coronary stenosis.

Twenty-six patients with left main coronary (LMC) stenosis were operated upon with preoperative intra aortic balloon pump (IABP) support. There was no mortality, and no morbidity attributable to the balloon catheter. The most delicate facet of revascularization surgery in this entity is the pre-cardiopulmonary bypass phase including anesthesia induction during which blood pressure fluctuation may further diminish severely compromised coronary flow. Although systolic pressure dropped to below 100 mm Hg in 50% of patients during induction, there were only two patients with electrocardiographic evidence of perioperative myocardial infarction, and only one who needed rantic institution of cardiopulmonary bypass just after induction. Perioperative logistics were quite trouble free in all 26 patients, in marked contrast to 5 LMC patients operated upon prior to our preoperative IABP concent; 3 of these deteriorated upon induction, with two deaths resulting. Preoperative IABP is a reasonable supportive adjunct in surgery for LMC stenosis.     

Improvement in thoracic aortic pressure after proximal aortic cross-clamping by balloon occlusion of the distal aorta

Spinal cord hypoperfusion injury is a devastating complication of cross-clamping the proximal thoracic aorta. The collateral circulation around the cross-clamp is generally poorly developed, and the run-off is immense, resulting in extremely low thoracic aortic and spinal cord perfusion pressures. The authors postulated that balloon occlusion of the abdominal aorta might confine this reduced collateral flow around the cross-clamp to the thoracic aorta. In 8 of 16 dogs subjected to aortic cross-clamping of the aorta just beyond the arch vessels, the abdominal aorta was also occluded by a balloon. Thoracic aortic pressure and spinal cord perfusion pressure were significantly higher in the animals with aortic balloon occlusion than in those without balloon occlusion (77 +/- 8 mm Hg versus 26 +/- 1 mm Hg, p less than 0.01, and 67 +/- 8 mm Hg versus 18 +/- 2 mm Hg, p less than 0.01, at 10 minutes after cross-clamping). Abdominal aortic balloon occlusion increases thoracic aortic pressure after the aorta is cross-clamped proximally. Further studies are necessary in primates to assess the effect of this procedure in spinal cord perfusion and the rate of paraplegia.     

Comparison of regional myocardial blood flow and metabolism distal to a critical coronary stenosis in the fibrillating heart during alternate periods of pulsatile and nonpulsatile perfusion

The effect of pulsatile cardiopulmonary bypass on intramyocardial gas tensions and regional myocardial blood flow was studied in 10 mongrel dogs. Following application of a critical stenosis to the circumflex coronary artery (CIRC), animals were placed on total bypass with vented, fibrillating hearts. During three 45 minute periods of perfusion, animals alternately received pulsatile or linear flow with perfusion pressure carefully maintained at 80 mm. Hg. In myocardium supplied by the stenosed CIRC, intramyocardial oxygen tension (PO2) rose from 13 +/- 3 to 19 +/- 5 mm. Hg when a period of linear flow was followed by a period of pulsatile flow (p less than 0.025). Similarly in the CIRC-supplied area, intramyocardial carbon dioxide (PCO2) decreased from 128 +/- 12 to 99 +/- 12 mm. Hg (p less than 0.005) with conversion from linear to pulsatile flow. Myocardial blood flow (microsphere technique) to endocardial and epicardial layers of the CIRC-supplied area was significantly greater (p less than 0.05) during pulsatile than during linear perfusion. In contrast, when periods of pulsatile bypass were followed by periods of linear perfusion, myocardial PO2 fell from 25 +/- 6 to 9 +/- 3 (less than 0.02) and myocardial PCO2 rose from 82 +/- 12 to 154 +/- 12 mm. Hg (p less than 0.001). These data suggest that (1) fibrillation-induced regional ischemia distal to a critical coronary stenosis can be reduced by pulsatile perfusion during bypass and (2) the mechanism for the reduction in regional ischemia is improved myocardial blood flow.     

An Aortic Balloon Catheter Incorporating a Conduit for Percutaneous Cardiopulmonary Support

Circulatory support using both intraaortic balloon pumping (IABP) and percutaneous cardiopulmonary support (PCPS) can improve general hemodynamics; however, sometimes brain damage occurs caused by hypoperfusion. Such cerebral hypoperfusion is likely to be caused by PCPS when applying the conventional femoral cannulation. We have developed a new IABP catheter which incorporates a conduit for PCPS with an outlet at the catheter tip, the goal of which is the improvement of cerebral perfusion. The hemodynamic characteristics of this new IABP catheter were compared with those of the conventional combination of IABP and PCPS. Studies were performed by mock test using a pulsatile artificial heart. A polyvinyl chloride tube acted as the aorta with 2 branches at the proximal and distal portions representing the upper and lower portions of the body. The IABP balloon was positioned between the 2 branches, and changes in flow at the 2 branches were examined at varying PCPS flow rates. Flow in the proximal branch using the new device was greater than it was using the conventional PCPS device. We conclude that cerebral perfusion could be improved with the use of this new special IABP catheter.     

Intra‐Aortic Balloon Pump Support in the Isolated Beating Porcine Heart in Nonischemic and Ischemic Pump Failure

The blood pressure changes induced by the intra‐aortic balloon pump (IABP) are expected to create clinical improvement in terms of coronary perfusion and myocardial oxygen consumption. However, the measured effects reported in literature are inconsistent. The aim of this study was to investigate the influence of ischemia on IABP efficacy in healthy hearts and in shock. Twelve slaughterhouse porcine hearts (hearts 1–12) were connected to an external circulatory system, while physiologic cardiac performance was restored. Different clinical scenarios, ranging from healthy to cardiogenic shock, were simulated by step‐wise administration of negative inotropic drugs. In hearts 7–12, severe global myocardial ischemia superimposed upon the decreased contractile states was created. IABP support was applied in all hearts under all conditions. Without ischemia, the IABP induced a mild increase in coronary blood flow and cardiac output. These effects were strongly augmented in the presence of persisting ischemia, where coronary blood flow increased by 49 ± 24% (P < 0.01) and cardiac output by 17 ± 6% (P < 0.01) in case of severe pump failure. As expected, myocardial oxygen consumption increased in case of ischemia (21 ± 17%; P < 0.01), while it slightly decreased without (?3 ± 6%; P < 0.01). In case of progressive pump failure due to persistent myocardial ischemia, the IABP increased hyperemic coronary blood flow and cardiac output significantly, and reversed the progressive hemodynamic deterioration within minutes. This suggests that IABP therapy in acute myocardial infarction is most effective in patients with viable myocardium, suffering from persistent myocardial ischemia, despite adequate epicardial reperfusion.