Effects Of Intra-aortic Counterpulsation Research Articles

Effects of Intra-Aortic Counterpulsation on Aortic Wall Energetics and Damping: In Vivo Experiments

Intra-aortic balloon pumping (IABP) could modify the arterial biomechanics; however, its effects on arterial wall properties have not been fully explored. This dynamical study was designed to characterize the pressure-dependent and smooth muscle-dependent effects of IABP on aortic wall energetics in an in vivo animal model. Intra-aortic balloon pumping (1:2) was performed in six anesthetized sheep in which aortic pressure and diameter signals were measured in basal, augmented (during balloon inflation), and assisted (postaugmented) beats. Energy dissipation values in augmented and assisted beats were significantly higher than those observed in basal state (p < 0.05). Assisted beats showed a significant increase of wall damping with respect to basal and augmented beats (p < 0.05). Intra-aortic balloon pumping resulted in a significant increase of pulse wave velocity (p < 0.05) in augmented beats with respect to basal state (6.3 +/- 0.8 vs. 5.2 +/- 0.5 m x s(-1)); whereas values observed in assisted beats were significantly (p < 0.05) lower than those observed in augmented beats (4.9 +/- 0.5 vs. 6.3 +/- 0.8 m x s(-1)). Our findings show that IABP determined the pressure and smooth muscle-dependent changes in arterial wall energetics and damping properties in this animal model.

Effects of intraaortic balloon counterpulsation on middle cerebral artery blood flow velocities

The intraaortic balloon pump has been shown to improve cardiac output and diastolic coronary flow. The aim of our study was to determine the effects of intraaortic counterpulsation (IABP) on cerebral blood flow velocities measured on the middle cerebral artery.

Catecholamine Infusion versus Intraaortic Counterpulsation at the Initial Phase of Left Intraventricular Balloon Pumping in the Fibrillating Animal Heart

This experimental study compares the effect of catecholamine infusion to the effect of intraaortic counterpulsation (IABP) while initiating intraventricular balloon pumping (IVBP) in the fibrillating heart. In 12 dogs IVBP started immediately after the induction of ventricular fibrillation. Intravenous adrenaline or noradrenaline (at a progressively increasing infusion rate until the systolic aortic blood pressure was 120 mm Hg) was interchanged with IABP. The systolic aortic pressure, the aortic flow and the mean left atrial pressure were, respectively, 120.4 +/- 0.5 mm Hg, 42 +/- 4 ml kg-1 min-1 and 18.7 +/- 1.2 mm Hg (x +/- SEM) ten min after initiating catecholamine infusion and 97 +/- 5 mm Hg (with a 131 +/- 4 mm Hg diastolic wave), 69.6 +/- 4 ml kg-1 min-1 and 16 +/- 1.5 mm Hg ten min after initiating IABP. The difference in aortic flow was significant (p < 0.001). The results indicate that a better aortic flow may be obtained by combining IVBP and IABP than IVBP and vasoconstrictive agents in the fibrillating heart. If IVBP, IABP and catecholamines are combined, both AF and AP may increase.

Effects of intraaortic balloon counterpulsation on regional myocardial function during acute coronary occlusion in the dog

The effects of intraaortic counterpulsation on regional myocardial function were studied using ultrasonic dimension gauges in 24 open chest dogs. Pairs of ultrasonic crystals were implanted in the subendocardium of the left ventricle in control, marginally ischemic and ischemic segments. After coronary arterial occlusion, the end-diastolic length of all three segments was increased. Segment shortening was rapidly replaced by systolic expansion in the ischemic segment. In the marginal segment, active shortening decreased by 53 percent and, in the control segment, shortening was augmented by compensatory operation of the Frank-Starling mechanism. Balloon pumping initiated 10 minutes after coronary occlusion resulted in an increase in mean aortic diastolic pressure from 103 to 115 mm Hg without any significant change in peak systolic pressure. In the marginal segment, end-diastolic length decreased by 3 percent, and previously reduced shortening increased to 82 percent of control value, deteriorating again with discontinuation of counterpulsation. Balloon pumping produced no change in the dyskinetic motion of the ischemic segment but caused compensatory augmentation of shortening of the control segment. Thus, counterpulsation selectively improved segment function of the marginally ischemic segment, presumably as a result of a regional increase in myocardial blood flow and in availability of oxygen due to augmented perfusion pressure. The systolic unloading effect was counterbalanced by improved cardiac performance.

Improved cardiac assistance with an aortic arch balloon.

The haemodynamic effects of intra-aortic counterpulsation with normally used cylindrical and newly designed aortic arch balloons on the coronary blood flow and the performance of the normal dog heart were compared. Both balloon types resulted in a decrease of left ventricular systolic and end-diastolic pressure, systolic arterial and end-diastolic arterial pressure. The amplitude of diastolic augmentation was significantly larger with the aortic arch balloon. The carotid artery flow increased significantly more with the aortic arch balloon (36%) than with the cylindrical balloon. Pulsation in the aortic arch effected a significant decrease in left ventricular impedance (33%), which was inversely correlated with a marked increment of the stroke volume (36%). In addition, mean coronary blood flow increased during aortic arch balloon pulsation (37%). From these data, it is concluded that optimal intra-aortic balloon pulsation should be performed with large balloons close to the aortic valve. The newly designed aortic arch balloon fulfils this condition.

The effects of intra-aortic counterpulsation on cardiac performance and metabolism in shock associated with acute myocardial infarction

The effect of intra-aortic counterpulsation (IACP, 22-94 hr) on hemodynamics and cardiac energetics was evaluated in 10 patients in shock after acute myocardial infarction. The data clearly indicate that IACP improves myocardial oxygenation, enhances peripheral perfusion, and probably improves myocardial contractility in the severely diseased heart. Before treatment, decreases in cardiac index (mean value, 1.22 liter/min per m(2)), systolic ejection rate (67 ml/sec), and time-tension index per minute (1280 mm Hg.sec/min) were observed. Systemic vascular resistance varied widely. Low coronary blood flow (68 ml/min per 100 g) was associated with increased myocardial oxygen extraction (79%), low coronary sinus oxygen tension (20 mm Hg), and abnormal myocardial lactate-pyruvate metabolism. During 4-6 hr of IACP, systolic pressure and left ventricular outflow resistance decreased by 18% and 24%, respectively, while cardiac index improved by 38%. Diastolic arterial pressure rose 98%. Increase in coronary blood flow from an average of 68 to 91 ml/100 g per min (P < 0.001) was significantly correlated with rise in mean arterial pressure (r = 0.685). This correlation was best expressed in a third-order curve, which intercepts the point of no flow at a mean aortic pressure of 30 mm Hg. The flow-pressure curve is relatively flat above 65-70 mm Hg, but becomes steeper as mean aortic pressure falls below this point. Myocardial oxygen consumption remained essentially unchanged during early IACP and tended to rise during the later stages. However, the relationship of cardiac work performed to oxygen availability was markedly improved. Myocardial lactate production of 6% shifted to 15% extraction (P < 0.001). After termination of IACP, hemodynamics and myocardial perfusion and metabolism remained improved in the four patients who could be reevaluated. Although the acute shock state was reversed in all patients, only one left the hospital. Extensive myocardial damage limits the long-term survival of such patients. Therefore early IACP seems desirable, when subtle evidence of pump failure after acute myocardial infarction occurs. Early use of IACP may prevent the development of severe coronary shock or may stabilize cardiac energetics in severe shock facilitating subsequent surgical intervention.

Effects of intra-aortic balloon counterpulsation on cardiac performance, oxygen consumption, and coronary blood flow in dogs.

The effect of intra-aortic Counterpulsation (IACP) with a balloon upon myocardial oxygen consumption (MV · o 2 ), coronary blood flow (TCF), and left ventricular performance was studied in 23 anesthetized canine right heart bypass preparations at constant heart rate and cardiac output. In nonhypotensive, nonTCF-limited preparations, IACP produced a fall in left ventricular peak systolic pressure (LVP) and a decrease in MV · o 2 (-1.1 ± 0.2 (SE) ml/min/100 g LV). In these animals there was little steady state change in TCF (-5.6±5.9 ml/min), secondary to autoregulation by the coronary vascular bed. Left ventricular end-diastolic pressure (LVEDP) fell if elevated but exhibited little change if initially normal. However, in hypotensive preparations, in which left ventricular performance was substantially limited by a decreased TCF, IACP produced a striking increase in TCF (+40.9 ± 8.6 ml/min) accompanied by an increase in MV · o 2 (+1.2±0.3 ml/min/100 g LV). Elevated LVEDPs fell substantially toward normal. Directionally similar changes in LVEDP could be produced by increasing TCF alone in the absence of balloon pumping. When TCF was maintained constant in the hypotensive, TCF-limited preparation, IACP produced a fall in peak LVP and LVEDP. These data document two effects of intra-aortic balloon Counterpulsation upon cardiac dynamics: (1) IACP can decrease left ventricular peak systolic pressure and LVEDP independent of changes in coronary flow; (2) a major effect of IACP in the hypotensive, failing, TCF-limited preparation is to improve cardiac performance by increasing TCF with an associated increase in MV · o 2 .