Biventricular pacing for weaning from extracorporeal circulation in heart failure

Permanent biventricular ICD-implantation in a heart failure second re-do-CABG patient: a case report

Biventricular pacing has been suggested in end-stage heart failure. We present a 59-year-old patient undergoing second re-do CABG (coronary artery bypass graft) and carotid artery endarterectomy. Ejection fraction was 15%, QRS-width 175 ms. Following the carotid and CABG procedure, an implanted single-chamber ICD (implantable cardioverter defibrillator) was upgraded to permanent biventricular DDD pacing by implantation of one epicardial left ventricular and one epicardial atrial electrode. At follow-up two months postoperatively ejection fraction had significantly improved to 45%, the patient underwent stress test with adequate load and reported a good quality of life.

Impact of Different Pacing Modes on Left Ventricular Contractility Following Cardiopulmonary Bypass

BACKGROUND

Acute left ventricular (LV) dysfunction after cardiopulmonary bypass (CBP) is a serious complication in cardiac surgery. The aim of this study was to investigate the effect of different epicardial pacing modes on LV contractility and changes of myocardial oxygen extraction (MVO(2)) following CPB in an animal model. The utility of conductance catheter measurement versus left ventricular outflow tract mean systolic acceleration (LVOT(Acc)) for quantification of LV function was evaluated.

METHODS

Fourteen piglets underwent median sternotomy and CPB for 90 minutes, myocardial ischemia for 60 minutes, and reperfusion for 30 minutes. Different pacing modes were obtained before and after CPB to investigate changes in LV function. LV Function was quantified by end-systolic-pressure-volume relationships (ESPVR) as measured by the conductance catheter method and by LVOT(Acc) obtained from transepicardial echocardiographic studies.

RESULTS

LV contractility improved significantly by biventricular and atrial pacing compared with natural sinus rhythm (SR). MVO(2) remained stable or even decreased with biventricular pacing after surgery compared with SR. Right ventricular pacing resulted in poor LV-function with a rise of MVO(2). LVOT(Acc) showed a strong correlation to invasively measured ESPVR.

CONCLUSION

Postoperative biventricular pacing was associated with an improved LV contractility without rise of MVO(2) compared with SR and atrial pacing. At termination of CPB, this appears to facilitate the management of LV failure and potentially may reduce the need for inotropic support, additionally protecting myocardial metabolism. The echocardiographic assessment of LVOT(Acc) was a simple and reliable as well as effective method to quantify LV contractility and showed a good correlation with the more invasive conductance catheter.

Perioperative Biventricular Pacing Leads to Improvement of Hemodynamics in Patients with Reduced Left-Ventricular Function?Interim Results

BACKGROUND

Cardiac resynchronization therapy (CRT) has been introduced as a new therapeutic modality in patients with chronic heart failure. However, most studies have investigated the hemodynamic effects in congestive, but not postoperative heart failure.

OBJECTIVE

The following study investigates hemodynamic effects of perioperative temporary biventricular pacing in patients undergoing open heart surgery. In 54 patients one left and one right ventricular epicardial wire was placed during open heart operations. Hemodynamic parameters were measured immediately after the operation and 6 as well as 24 hours postoperatively. Transesophageal echocardiography was performed 1 hour postoperatively.

RESULTS

Of the 54 patients (59.2%), 32 responded to biventricular pacing with an increase in cardiac output; in these patients synchronized ventricular contraction could be verified echocardiographically. This hemodynamic benefit persisted 6 hours and 24 hours postoperatively. The remaining 22 patients did not show any hemodynamic improvement from biventricular stimulation.

CONCLUSION

Biventricular pacing leads to significant rise in cardiac output in approximately 59% of patients with severely reduced left ventricular function and widened QRS complexes. Further studies are necessary to define clearly the clinical characteristics of patients who show remodeling by CRT.

Cardiac resynchronisation therapy for heart failure

Cardiac resynchronisation therapy (CRT) reduces symptoms and improves left ventricular function in chronic heart failure (CHF) patients with left ventricular systolic dysfunction and prolonged QRS duration. Recent studies have demonstrated a reduction in mortality associated with CRT. When combined with an implantable cardioverter defibrillator (ICD) reduction in mortality is likely to reduce further. Cardiac resynchronisation therapy is well tolerated and free from compliance issues and therefore should be considered for all suitable patients. Identifying patients who will derive maximum benefit requires further study and has health economic implications. We review here the CRT trial evidence as well as the implantation technique and complications. We also describe a case report where an intra-aortic balloon pump was used successfully as a bridge to CRT to treat a patient with end-stage heart failure.

Echocardiographic Assessment of Ventricular Asynchrony in Dilated Cardiomyopathy and Congenital Heart Disease: Tools and Hopes

Ventricular dyssynchrony is a relatively common problem in patients with heart failure, in particular those with wide QRS complex, and appears to have a deleterious effect on the natural history of heart failure, as it has been associated with increased mortality. Mechanistic studies, observational evaluations, and randomized trials have consistently demonstrated the beneficial effects of cardiac resynchronization therapy (CRT) in patients with moderate-to-severe chronic systolic heart failure and ventricular dyssynchrony who have failed optimal medical treatment. However, despite the promising results, it is estimated that in approximately 30% of patients undergoing CRT, the symptoms of heart failure do not improve or become even worse. One of the most important reasons for this failure is probably the lack of distinct mechanical dyssynchrony before implantation. A number of echocardiographic tools have been developed during the past 3 years for quantitative measurement of the severity of dyssynchrony before and after CRT. This review discusses the actual and potential role of different echocardiographic techniques in selection of patients and optimization of CRT and the value of some new clinical applications such as in congenital heart disease.

Acute Hemodynamic Benefit of Left Ventricular Apex Pacing in Children

BACKGROUND

Despite the fact that pacing at the right ventricular apex acutely and chronically decreases left ventricular contractile function, this pacing site is still conventionally used in adults and children. Because animal studies showed beneficial effects of left ventricular pacing, we compared the hemodynamic performance of left ventricular apex, left ventricular free wall, and right ventricular apex pacing in children.

METHODS

Studies were performed in 10 children (median age, 2.5 years; range, 2 months to 17 years) undergoing surgery for congenital heart disease with normal systemic left ventricular anatomy and intraventricular conduction. High-fidelity left ventricular and arterial pressure measurements were performed during epicardial right ventricular apex and left ventricular apex and free wall pacing.

RESULTS

Left ventricular apex pacing increased the maximum rate of rise of left ventricular pressure and pulse pressure significantly relative to right ventricular apex pacing (by 7.7% +/- 7.2% and 7.7% +/- 7.0%, respectively) without changes in end-diastolic left ventricular pressure. Left ventricular free wall pacing did not significantly improve hemodynamics as compared with right ventricular apex pacing. The QRS duration was not different among pacing at the three sites.

CONCLUSIONS

In this short-term study left ventricular apex pacing is hemodynamically superior to right ventricular apex and left ventricular free wall pacing in children. Therefore, the left ventricular apex appears a favorable pacing site after pediatric cardiac surgery.

Acute hemodynamic benefit of multisite ventricular pacing after congenital heart surgery

BACKGROUND

Cardiac dysfunction after congenital heart surgery is a major cause of morbidity and mortality. Cardiac resynchronization through multisite ventricular pacing (MSVP) improves cardiac index and ventricular function, and lowers systemic vascular resistance (SVR) in adults with heart failure and interventricular conduction delay.

METHODS

The acute hemodynamic effects of MSVP after congenital heart surgery were assessed. Twenty-nine patients (aged 1 week to 17 years) with prolonged QRS interval had atrial and ventricular unipolar epicardial temporary pacing leads placed at surgery. Group 1 consisted of patients with a single ventricle (n = 14); group 2 included patients with two-ventricle anatomy (tetralogy of Fallot, ventricular septal defect) undergoing ventricular surgery (n = 10); and group 3 included patients with two-ventricle anatomy undergoing other cardiac surgery (n = 5). At a mean postoperative day 1 (range, 0 to 6), blood pressure, systemic and mixed venous oxygen saturations, electrocardiograms, and echocardiograms were obtained before and after 20 minutes of MSVP.

RESULTS

The QRS duration decreased with MSVP in all patients (mean, 23%, p < 0.005). Systolic blood pressure improved in all patients (mean, 9.7%, p < 0.005). Cardiac index improved in 19 of 21 patients tested, with no change in 2 patients (mean, 15.1%, p = 0.0001). In 2 patients, MSVP facilitated weaning from cardiopulmonary bypass. Echocardiographic mitral or tricuspid valve inflow was not significantly different with MSVP.

CONCLUSIONS

Multisite ventricular pacing results in improved cardiac index and increased systolic blood pressure, and it can also facilitate weaning from cardiopulmonary bypass. Multisite ventricular pacing may be used as adjunct to standard postoperative treatment of cardiac dysfunction after congenital heart surgery.

Protect the heart in the intensive care unit--but how?

The heart plays a pivotal role in determining the oxygen supply to the body. As a result of its high oxygen extraction ratio, the myocardium must function efficiently to supply itself with oxygen. In the context of the ICU, the efficient functioning of the myocardium is confounded by a number of pathologic processes that may interfere with its oxygen supply or increase its oxygen demand. Conventional drug treatment of acute myocardial decompensation tends to increase myocardial oxygen demand. The myocardium may potentially be "protected" by treatment modalities that favorably alter the oxygen supply to demand ratio. Newer methods of protecting the heart may involve improving the coordination of myocardial contraction, using novel inotropic agents, supporting the myocardium metabolically, administrating blood products more conservatively, favorably altering the immune response, and using mechanical support devices. Myocardial protection may be improved by better use and understanding of monitors of myocardial performance.