Effects of intraaortic balloon counterpulsation on myocardial blood flow in patients with severe coronary artery disease

Intra-aortic balloon pump: Looking at the other side

Intra‐aortic balloon pump has been the most commonly employed cardiac assist device in the past, although, in recent years, its use in cardiogenic shock has been questioned. The pathophysiology of the proximal part of the balloon has been well studied, whereas, hemodynamics and flow below the distal portion of the balloon have not been fully understood yet. The distal flow contains a three‐wave flow pattern during diastolic balloon expansion: a flow reduction in early diastole, a backflow in mid‐diastole followed by a tele‐diastolic flow. More research on this topic is warranted to better understand the physics of the distal part of the balloon and its interaction with the three components of the local regulatory system: intrinsic (local metabolic and myogenic), extrinsic (autonomic nervous system), and humoral (local or circulating vasoactive substances). These new insights will be a guide for new balloon designs that will allow enhanced performance and improved outcomes.

Intra-aortic Balloon Counterpulsation for High-Risk Percutaneous Coronary Intervention: Defining Coronary Responders

The effect of intra-aortic balloon counterpulsation (IABC) varies, and it is unknown whether this is due to a heterogeneous coronary physiological response. This study aimed to characterise the coronary and left ventricular (LV) effects of IABC and define responders in terms of their invasive physiology. Twenty-seven patients (LVEF 31 ± 9%) underwent coronary pressure and Doppler flow measurements in the target vessel and acquisition of LV pressure volume loops after IABC supported PCI, with and without IABC assistance. Through coronary wave intensity analysis, perfusion efficiency (PE) was calculated as the proportion of total wave energy comprised of accelerating waves, with responders defined as those with an increase in PE with IABC. The myocardial supply/demand ratio was defined as the ratio between coronary flow and LV pressure volume area (PVA). Responders (44.4%) were more likely to have undergone complex PCI (p = 0.03) with a higher pre-PCI disease burden (p = 0.02) and had lower unassisted mean arterial (87.4 ± 11.0 vs. 77.8 ± 11.6 mmHg, p = 0.04) and distal coronary pressures (88.0 ± 11.0 vs. 71.6 ± 12.4 mmHg, p < 0.001). There was no effect overall of IABC on the myocardial supply/demand ratio (p = 0.34). IABC has minimal effect on demand, but there is marked heterogeneity in the coronary response to IABC, with the greatest response observed in those patients with the most disordered autoregulation.

How New Support Devices Change Critical Care Delivery

Mechanical support devices are used to support failing cardiac, respiratory, or both systems. Since Gibbon developed the cardiopulmonary bypass in 1953, collaborative efforts by medical centers, bioengineers, industry, and the National Institutes of Health have led to development of mechanical devices to support heart, lung, or both. These devices are used as a temporary or long-term measures for acute collapse of circulatory system and/or respiratory failure. Patients are managed on these support devices as a bridge to recovery, bridge to long term devices, or bridge to transplant. The progress in development of these devices has improved mortality and quality of life in select groups of patients. Care of these patients requires a multidisciplinary team approach, which includes cardiac surgeons, critical care physicians, cardiologists, pulmonologists, nursing staff, and perfusionists. Using a team approach improves outcomes in these patients.

Intra-aortic balloon counterpulsation in contemporary practice - where are we?

The intra-aortic balloon pump (IABP) remains the most widely used form of mechanical circulatory support in current clinical practice. This article will review the current evidence to guide IABP use, focussing on large registry and prospective, randomised data, and seek to establish appropriate roles for the IABP in contemporary practice. Despite a paucity of clinical evidence, the IABP remains a useful clinical tool in selected settings, although its routine, up-front use in relatively unselected MI populations is not supported by data. Although current evidence no longer supports routine use in certain high-risk groups, further studies of appropriately selected high-risk patients may yet demonstrate benefit in patients with moderate-severe degrees of shock.

Intra-aortic balloon pump in patients with cardiogenic shock complicating myocardial infarction: a systematic review and meta-analysis of randomized trials (protocol)

BACKGROUND

Cardiogenic shock is the leading cause of death in patients with acute myocardial infarction. Despite significant advancements in health technology and research, hospital mortality approaches 50%. The intra-aortic balloon pump is a mechanical hemodynamic assist device that has been used for over 40 years in the management of patients with cardiogenic shock. A recent randomized trial suggests that the use of intra-aortic balloon pumps does not reduce mortality in patients with ischemic cardiogenic shock.

METHODS

We plan to search MEDLINE, EMBASE, and the Cochrane Trial Registry for potentially eligible randomized trials that compare the use of intra-aortic balloon pump with no mechanical device support in patients with cardiogenic shock. No date, language or journal limitations will be applied. Two reviewers will independently screen and identify eligible studies using predefined eligibility criteria. Data abstraction will be done independently and in duplicate. We plan to use RevMan software to generate pooled estimates across included studies, using the previously published method of DerSimonian and Laird. We will report pooled estimates as risk ratios with 95% confidence intervals for binary outcomes, and as mean differences with 95% confidence intervals for continuous outcomes. We will assess the quality of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

DISCUSSION

The aim of this systematic review and meta-analysis is to summarize the available evidence on the efficacy of the intra-aortic balloon pump in cardiogenic shock. Systematic review registration: PROSPERO CRD42014007056.

Computational analysis of the effect of the type of LVAD flow on coronary perfusion and ventricular afterload

We developed a computational model to investigate the hemodynamic effects of a pulsatile left ventricular assist device (LVAD) on the cardiovascular system. The model consisted of 16 compartments for the cardiovascular system, including coronary circulation and LVAD, and autonomic nervous system control. A failed heart was modeled by decreasing the end-systolic elastance of the ventricle and blocking the mechanism controlling heart contractility. We assessed the physiological effect of the LVAD on the cardiovascular system for three types of LVAD flow: co-pulsation, counter-pulsation, and continuous flow modes. The results indicated that the pulsatile LVAD with counter-pulsation mode gave the most physiological coronary blood perfusion. In addition, the counter-pulsation mode resulted in a lower peak pressure of the left ventricle than the other modes, aiding cardiac recovery by reducing the ventricular afterload. In conclusion, these results indicate that, from the perspective of cardiovascular physiology, a pulsatile LVAD with counter-pulsation operation is a plausible alternative to the existing LVAD with continuous flow mode.

Effects of Intraaortic Balloon Pumping on the Angiographic No-Reflow Phenomenon After Percutaneous Coronary Intervention in Patients With Anterior Myocardial Infarction

BACKGROUND

The effects of intraaortic balloon pumping (IABP) are considered to be a reduction in myocardial oxygen demand because of systolic left ventricular unloading and an increase in coronary blood flow. Although the former effect has been consistently recognized, the latter effect remains controversial. The purpose of this study was to examine the effects of IABP on the angiographic no-reflow phenomenon.

METHODS AND RESULTS

The coronary flow velocity pattern of the left anterior descending artery (LAD) was assessed by transthoracic Doppler echocardiography during IABP counterpulsation, and the effects of IABP were compared between angiographic no-reflow and good reflow patients. The study group comprised 17 patients with anterior myocardial infarction who underwent percutaneous coronary intervention and IABP for typical clinical indications. Echocardiographic data were obtained during 2:1 balloon pumping after coronary angioplasty. In the good reflow group (n=9), IABP counterpulsation increased the mean diastolic flow velocity (MDFV) and peak diastolic flow velocity (PDFV) by 56 +/- 32% (p<0.001) and 48 +/- 27% (p<0.001), respectively. In contrast, in the no-reflow group (n=8), IABP only increased the MDFV and PDFV by 19 +/- 33% (p=0.24) and 6 +/- 12% (p=0.22), respectively. Diastolic deceleration time was smaller and the prevalence of systolic retrograde flow was greater in the no-reflow group than in the good reflow group, and IABP affected neither parameter.

CONCLUSIONS

IABP had limited effects on LAD flow velocity pattern in patients with the angiographic no-reflow phenomenon.

Enhanced coronary flow velocity during intra-aortic balloon pumping assessed by transthoracic doppler echocardiography

OBJECTIVES

The study was done to determine potential utility of measuring coronary flow velocity (CFV) by transthoracic Doppler echocardiography (TTDE) during intra-aortic balloon pumping (IABP).

BACKGROUND

Use of IABP has been shown to increase CFV assessed by an invasive technique. The CFV in the left anterior descending coronary artery (LAD) can be measured by TTDE.

METHODS

Coronary flow velocity in the distal LAD by TTDE was measured in 40 critically ill patients requiring IABP. All patients received emergency coronary angiography. Both CFV and pressure data were obtained during 1:2 balloon pumping.

RESULTS

Adequate diastolic CFV recording was obtained in all patients. The IABP decreased systolic pressure and increased diastolic pressure. Average peak diastolic flow velocity and diastolic velocity time integral was 19 +/- 11 cm/s and 7.7 +/- 4.4 cm with non-augmented beat. These values were increased significantly (61 +/- 38%, 59 +/- 35%, p < 0.001) with augmented beat. Significant correlation was noted between % diastolic pressure augmentation and % increase in diastolic CFV (r = 0.62 to 0.69, p < 0.001). There was no significant difference in flow enhancement during IABP, irrespective to the proximal LAD stenosis severity (severe stenosis: 73 +/- 70%; intermediate stenosis: 61 +/- 29%; no significant stenosis: 58 +/- 29%; p = NS, analysis of variance). By continuous recording of CFV, the optimal timing of balloon control could be adjusted to maximize flow velocity during augmentation.

CONCLUSIONS

Use of TTDE can be employed in monitoring CFV augmentation during IABP. The IABP produced significant distal flow enhancement even in patients with critical proximal stenosis. This totally noninvasive approach may help to optimize the benefits of IABP for coronary flow augmentation.

Hemodynamic effects of new intra-aortic balloon counterpulsation timing methods in patients: a multicenter evaluation

BACKGROUND

To test whether later intra-aortic balloon pump (IABP) deflation approaching or simultaneous with left ventricular ejection would improve hemodynamics and myocardial efficiency with the use of new balloon deflation methods, 4 IABP timing techniques were evaluated in 43 patients.

METHODS AND RESULTS

Later balloon deflation produced significantly greater percentage changes in mean aortic pressure (6% vs 1%), systolic pressure time index (-27% vs -20%), diastolic pressure time index (35% vs 19%), and the systolic pressure-time index/diastolic pressure-time index ratio (97% vs 51%), respectively. However, these changes increased peak systolic pressure (-15% vs -11%). Cardiac output and stroke volume indexes were not significantly altered over the 4 settings.

CONCLUSIONS

These data suggest that systemic hemodynamics and myocardial efficiency may be improved by later balloon deflation approaching left ventricular ejection in comparison to conventional IABP timing.

The use of intraaortic balloon counterpulsation in acute myocardial infarction and high risk coronary angioplasty

Patients with complex coronary arterial stenoses, decreased ejection fraction, or acute myocardial infarction are at increased risk during percutaneous coronary interventions. Intraaortic balloon counterpulsation (IABP) can provide benefit in such cases by several mechanisms. Myocardial perfusion is improved and left ventricular afterload is reduced by balloon counterpulsation. Patients with cardiogenic shock clearly benefit from balloon counterpulsation until revascularization can be performed. Recent studies have documented the utility of balloon counterpulsation in patients undergoing angioplasty as treatment for an acute myocardial infarction. Balloon counterpulsation is also an effective means to reduce ischemia and provide hemodynamic support during complex percutaneous coronary interventions. This review will summarize the benefits, indications, and complications of balloon counterpulsation during acute myocardial infarction and high-risk coronary angioplasty.

Intraaortic balloon counterpulsation enhances coronary thrombolysis induced by intravenous administration of a thrombolytic agent

OBJECTIVES

This study was designed to test the hypothesis that in the presence of moderate hypotension, intraaortic balloon counterpulsation would enhance coronary thrombolysis induced by intravenous administration of recombinant tissue-type plasminogen activator (rt-PA).

BACKGROUND

Although many studies have confirmed the efficacy of thrombolytic therapy in acute myocardial infarction, few have systematically investigated the effects of alterations in aortic pressure on coronary thrombolysis, and none have previously investigated the effects of intraaortic balloon counterpulsation on thrombolysis.

METHODS

The effects of intraaortic balloon counterpulsation on aortic pressure, coronary blood flow and coronary thrombolysis were studied in a canine model. Coronary thrombosis was induced in eight dogs by injection of radioactive blood clot through a catheter placed in the left anterior descending coronary artery. Subsequently, dogs underwent phlebotomy to decrease systolic aortic pressure to approximately 90 mm Hg. After phlebotomy, during a 15-min interval of intravenous administration of rt-PA, coronary thrombolysis and coronary flow were determined during and in the absence of counterpulsation.

RESULTS

Intraaortic balloon counterpulsation significantly increased aortic diastolic pressure. Corresponding to the increase in pressure, intraaortic balloon counterpulsation significantly increased the rate of rt-PA-induced coronary thrombolysis. Although not statistically significant, peak diastolic coronary flow tended to increase with counterpulsation.

CONCLUSIONS

These results indicate that in the presence of moderate systemic hypotension, intraaortic balloon counterpulsation enhances the rate of rt-PA-induced coronary thrombolysis.

Augmentation of coronary blood flow by intra-aortic balloon pumping in patients after coronary angioplasty

BACKGROUND

Controversy exists regarding the ability of intra-aortic balloon pumping to increase coronary blood flow in patients with obstructive coronary artery disease. To assess the effects of intra-aortic balloon pumping on coronary hemodynamics, we measured coronary blood flow velocity with a 0.018-in. Doppler-tipped angioplasty guide wire in 15 patients who received an intra-aortic balloon pump for typical clinical indications.

METHODS AND RESULTS

Intra-aortic balloon pumping augmented diastolic pressure 83 +/- 35%. In nine patients before angioplasty, peak diastolic coronary flow velocity beyond the stenosis (mean diameter narrowing, 95 +/- 7%) was 5.3 +/- 9.6 cm/sec and was unaffected by intra-aortic balloon pumping. After angioplasty, the improved coronary luminal diameter narrowing (n = 12; mean narrowing, 18 +/- 12%) was associated with increased distal diastolic flow velocity integral and peak diastolic and mean velocities (13.3 +/- 8.4 units: 36.4 +/- 18.3 and 24.0 +/- 11.4 cm/sec, respectively; all p < 0.01 versus before angioplasty), which were further augmented (36 +/- 37%, 54 +/- 49%, and 26 +/- 17%, respectively; all p < 0.01) with intra-aortic balloon pumping. Intra-aortic balloon pumping did not significantly increase the distal systolic velocity integral (10 +/- 59%) or peak systolic velocity (3 +/- 33%). Similar degrees of balloon pump augmentation of distal coronary flow velocity values were observed in five angiographically normal reference arteries in four patients.

CONCLUSIONS

These data demonstrate lack of significant flow improvement beyond most critical stenoses with intra-aortic balloon pumping and the unequivocal restoration and intra-aortic balloon pump-mediated augmentation of both proximal and distal coronary blood flow velocities after amelioration of severe coronary obstructions in patients after successful coronary angioplasty.

Enhanced coronary blood flow velocity during intraaortic balloon counterpulsation in critically ill patients

OBJECTIVES

The aim of this study was to assess coronary blood flow during intraaortic balloon counterpulsation by direct measurement.

BACKGROUND

In a majority of human studies, increased coronary blood flow during intraaortic balloon counterpulsation measured by indirect techniques has not been consistently demonstrated.

METHODS

Hemodynamic variables and coronary blood flow velocity (20-MHz Doppler-tipped catheter) data were measured in 19 patients requiring intraaortic balloon pumping for clinical indications (11 patients had acute myocardial infarction [9 with shock], 6 had unstable angina, 1 had acute mitral regurgitation and 1 was at high risk undergoing angioplasty). Hemodynamic data, mean and phasic diastolic flow velocity and velocity-time integrals (computed from digitized waveforms) were analyzed during periods of 1:1 balloon counterpulsation.

RESULTS

Intraaortic balloon pumping decreased systolic pressure (6 +/- 10%, p < 0.001) and increased diastolic pressure (80 +/- 30% from baseline, p < 0.001) without changing RR interval. Peak phasic, mean coronary flow velocity and diastolic flow velocity integral were significantly increased (115 +/- 115%, 67 +/- 61%, 103 +/- 81%, respectively, all p < 0.001) during intraaortic balloon pumping. In addition, although a wide splay of data was evident due to operator set variations in balloon inflation and deflation timing, the greater increases in diastolic flow velocity integral (DFVi) occurred in patients with basal systolic pressure < or = 90 mm Hg (% delta DFVi = 102 - 0.1.[unaugmented systolic pressure], SEE = 21.7 mm Hg, r = 0.30, p < 0.001).

CONCLUSIONS

Intraaortic balloon pumping unequivocally and significantly augments proximal coronary blood flow velocity, nearly doubling the coronary flow velocity integral in most patients. This mechanism may be a significant means of ischemia relief in hypotensive patients.

Effects of pulsed external augmentation of diastolic pressure on coronary and systemic hemodynamics in patients with coronary artery disease

The purpose of this study was to define the effects of pulsed external diastolic pressure augmentation on coronary and systemic hemodynamics in 14 men with coronary artery disease and normal left ventricular function. Coronary sinus and great vein blood flow (thermodilution) and systemic hemodynamics were measured before, during, and after timed lower extremity compression, augmenting peak diastolic pressure to within 5 mm Hg of systolic pressure. Systolic and diastolic pressure-time indices were calculated from the high-fidelity micromanometer left ventricular-aortic recordings. External counterpulsation increased mean arterial pressure (108 +/- 11 [1 SD] to 114 +/- 12 mm Hg, p less than 0.01) and the diastolic pressure-time index (440 +/- 51 to 498 +/- 82 units, p less than 0.01), with no change in the systolic pressure-time index, absolute coronary sinus, or great cardiac vein blood flow. External diastolic pressure augmentation did not affect heart rate, right heart hemodynamics, cardiac output, or calculated myocardial oxygen consumption. An unanticipated finding was a greater than or equal to 10% reduction in peak systolic pressure during external diastolic pressure augmentation in 8 of 14 patients. Despite minimal changes in absolute myocardial blood flow and oxygen consumption, the increase in the diastolic pressure-time/systolic pressure-time index ratio suggests that subendocardial perfusion may be favorably influenced by diastolic pressure augmentation and may explain the previously reported clinical benefits of external counterpulsation in some patients with ischemic heart disease.

Myocardial perfusion after aortocoronary bypass surgery: measurements at rest and after administration of isoproterenol

This study examined quantitative regional myocardial perfusion (RMP) measured by the washout of 133Xe at rest and after an isoproterenol challenge in 50 patients (group I) studied 8 to 14 days after they underwent saphenous vein bypass grafting to the left coronary artery, and compared this with RMP measured in the native left coronary artery in 14 patients (group II) with significant coronary artery disease and in 12 normal subjects (group III). The double product of the heart rate and aortic systolic pressure was used as an indicator of demand. The statistical significance of group comparisons was analyzed with Dunn's multiple comparisons among means test. Analysis of the data showed no significant difference among the groups with respect to aortic systolic pressure. In subjects at rest, heart rate was lower in groups II and III than in group I, and double product was lower in group II than in group I. After isoproterenol, both heart rate and double product were lower in group II compared with groups I and III, but there was no significant difference between groups I and III with respect to heart rate or double product. Mean resting RMP in group II was lower than in group I; however, results of other group comparisons were insignificant for resting parameters. After isoproterenol, mean flow (ml/100 g/min) in group I was similar to flow in group III (130 +/- 24 vs 139 +/- 26). In contrast, the average flow response after isoproterenol was significantly less in group II when compared with that in group I (105 +/- 20 vs 130 +/- 24) and with that in group III (105 +/- 20 vs 139 +/- 26). Because of differences in levels of demand with isoproterenol, the change in flow was normalized to the percent increase in double product. These data showed results similar to those above, i.e., normalized RMP in patients with coronary artery disease was significantly lower than that in normal subjects (82 +/- 41 vs 119 +/- 57) and in revascularized patients (82 +/- 41 vs 105 +/- 54). However, there was no significant difference between normal subjects and patients who had undergone surgery. To further evaluate the relationship of flow response to demand parameters, we plotted RMP/double product vs resistance. The data revealed a significant correlation between these variables in all groups both in subjects at rest and after isoproterenol.(ABSTRACT TRUNCATED AT 400 WORDS)