Relation of hemodynamic variables to augmentation of left anterior descending coronary flow by intraaortic balloon pulsation in coronary artery disease

Role of acute mechanical circulatory support devices in cardiogenic shock

Cardiogenic shock is a state of low cardiac output that is associated with significant morbidity and mortality. A considerable proportion of patients with cardiogenic shock respond poorly to medical management and require acute mechanical circulatory support (AMCS) devices to improve tissue perfusion as well as to support the heart. In the last two decades, many new AMCS devices have been introduced to support the right, left, and both ventricles. All these devices vary in terms of the support they provide to the body and heart, mechanism of functioning, method of insertion, and adverse events. In this review, we compare and contrast the available percutaneous and surgically placed AMCS devices used in cardiogenic shock and discuss the associated clinical and hemodynamic data to make a conscious decision about choosing a device.

Intra-aortic balloon pump timing: review of evidence supporting current practice

Intra-aortic balloon counterpulsation is the most widely used therapy for support of a compromised left ventricle. The principles of counterpulsation were developed in the 1950s, and intra-aortic balloon pumps have been used for more than 40 years. Despite this long-standing clinical use, many of the timing practices have continued almost unchanged from their inception. One of the most important aspects of the pumps is timing, or synchronizing the action of the device with the cardiac cycle. The principles of timing are based on the physiological objectives of counterpulsation; however, research into alternative timing methods has led to conflicting and often confusing information on the appropriate timing method for a specific clinical situation or patient. Although a body of knowledge is available, much of the research is dated and covers only specific timing methods or populations of patients. Further evidence is needed to support the selection of timing methods and determine the clinical benefits of the various methods.

Chronic extra-aortic balloon counterpulsation: first-in-human pilot study in end-stage heart failure

BACKGROUND

Some patients continue to have significant heart failure symptoms despite optimal medical therapy.

METHODS

We describe a first-in-human experience with an implantable non-blood-contacting extra-ascending aortic counterpulsation heart assist system (C-Pulse) in 5 end-stage heart failure patients, aged 54 to 73 years.

RESULTS

All patients improved by 1 NYHA class and improvements in invasive hemodynamics were documented in 3 patients. Three of 5 patients (60%) had infectious complications. Two patients were explanted at 5 and 7 weeks, respectively, as a result of mediastinal infection related to the implant procedure. One patient was successfully transplanted at 1 month and 1 remained hemodynamically improved on the device at 6 months but suffered infective complications. The device and protocol have been modified as a result of this pilot study with a further multicenter safety study underway.

CONCLUSIONS

Although feasibility of this device is suggested by this pilot study, safety and efficacy will need to be examined in a larger cohort with longer follow-up.

Understanding the C-pulse device and its potential to treat heart failure

The Sunshine Heart C-Pulse (C-Pulse; Sunshine Heart Inc., Tustin, CA) device is an extra-aortic implantable counterpulsation pump designed as a non-blood contacting ambulatory heart assist device, which may provide relief from symptoms for class II-III congestive heart failure patients. It has a comparable hemodynamic augmentation to intra-aortic balloon counterpulsation devices. The C-Pulse cuff is implanted through a median sternotomy, secured around the ascending aorta, and pneumatically driven by an external system controller. Pre-clinical studies in the acute pig model, and initial temporary clinical studies in patients undergoing off-pump coronary bypass surgery have shown substantial increase in diastolic perfusion of the coronary vessels, which translated to a favorable improvement in ventricular function. A U.S. prospective multi-center trial to evaluate the safety and efficacy of the C-Pulse in class III patients with moderate heart failure is now in progress.

Effects of left ventricular unloading by Impella recover LP2.5 on coronary hemodynamics

OBJECTIVES

We studied the effects of LV unloading by the Impella on coronary hemodynamics by simultaneously measuring intracoronary pressure and flow and the derived parameters fractional flow reserve (FFR), coronary flow velocity reserve (CFVR), and coronary microvascular resistance (MR).

BACKGROUND

Patients with compromised left ventricular (LV) function undergoing high-risk percutaneous coronary intervention (PCI) may benefit from LV unloading. Limited information is available on the effects of LV unloading on coronary hemodynamics.

METHODS

Eleven patients (mean LV ejection fraction of 35 +/- 11%) underwent PCI during LV support by the LV unloading device (Impella Recover LP2.5). Intracoronary measurements were performed in a nonstenotic coronary artery after the PCI, before and after adenosine-induced hyperemia at four different support levels (0-2.5 L/min).

RESULTS

Aortic and coronary pressure increased with increasing support levels, whereas FFR remained unchanged. Baseline flow velocity remained unchanged, while hyperemic flow velocity and CFVR increased significantly with increasing support levels (61 +/- 24 to 72 +/- 27 cm/sec, P = 0.001 and 1.88 +/- 0.52 to 2.34 +/- 0.63, P < 0.001 respectively). The difference between baseline MR and hyperemic MR significantly increased with increasing support levels (1.28 +/- 1.32 to 1.89 +/- 1.43 mm Hg cm(-1) sec, P = 0.005).

CONCLUSIONS

Unloading of the LV by the Impella increased aortic and intracoronary pressure, hyperemic flow velocity and CFVR, and decreased MR. The Impella-induced increase in coronary flow, probably results from both an increased perfusion pressure and a decreased LV volume-related intramyocardial resistance.

Extra-aortic balloon counterpulsation: an intraoperative feasibility study

BACKGROUND

Current methods of counterpulsation or ventricular assistance have significant vascular and limb complications. The aim of this study was to determine the safety and performance of a new method of non-blood-contacting counterpulsation using an inflatable cuff around the ascending aorta (extra-aortic balloon [EAB]).

METHODS AND RESULTS

In 6 patients undergoing first time off-pump coronary bypass surgery via sternotomy, the EAB was secured around the ascending aorta and attached to a standard counterpulsation console. At baseline and with 1:2 and 1:1 augmentation, hemodynamic and echocardiographic parameters of ventricular function and coronary flow were measured. High-intensity transient signals were measured using transcutaneous Doppler over the right common carotid artery. No complications occurred. With EAB there was no significant change in heart rate or blood pressure and no increase in high-intensity transient signals. There was a 67% increase in diastolic coronary blood flow (mean left-main diastolic velocity time integral 15.3 cm unassisted versus 25.1 cm assisted, P<0.05). Measurements with transesophageal echocardiography at baseline and with 1:1 counterpulsation demonstrated a 6% reduction in end-diastolic area (P=NS), a 16% reduction in end-systolic area (P<0.01), a 31% reduction in left ventricular wall stress (P<0.05), and a 13% improvement in fractional area change (P<0.005).

CONCLUSIONS

EAB counterpulsation augments coronary flow and reduces left ventricular afterload. Further testing is warranted to assess the use of the EAB for chronic non-blood-contacting support of the failing heart.

Extra-Ascending Aortic Versus Intra-Descending Aortic Balloon Counterpulsation—Effect on Coronary Artery Blood Flow

BACKGROUND

Diastolic counterpulsation has been used to provide circulatory augmentation for chronic heart failure or for short-term cardiac support. Recently an extra-aortic balloon (EAB) counterpulsation device has been proposed.

AIM

To compare the circulatory effects of counterpulsation using the EAB or an intra-aortic balloon (IAB) in the acute pig model.

METHODS

In six anaesthetized great white pigs (paced at 100 bpm), ECG, arterial and central venous pressures, flow in the coronary circulation and descending thoracic aorta were measured. Baseline data was collected, then with the EAB or an IAB fitted using 1:1 and 1:2 counterpulsation modes. Baseline data was compared to EAB and IAB data in 1:1 mode. Assisted beat data compared to unassisted beat data was also analysed in 1:2 mode.

RESULTS

Both devices augmented peak diastolic arterial pressure, and decreased afterload. EAB counterpulsation increased diastolic coronary flow in both the 1:1 mode by 69% (p < 0.05) and in the 1:2 mode by 63% (assisted versus unassisted beat, p < 0.05). The IAB significantly increased diastolic coronary flow only in the 1:2 mode by 28% (p < 0.01). Both devices augmented total coronary flow and some augmentation of aortic flow was observed.

CONCLUSION

The circulatory effect of the EAB and IAB counterpulsation were comparable. This suggests the EAB could be used as a non-blood contacting heart assist device in patients suffering moderate-severe heart failure.

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 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.