Acute pulmonary edema induced by left bundle branch block

[Left bundle branch block - dilated cardiomyopathy - heart failure: common links in the closed pathogenetic chain]

This review summarizes the available information on the epidemiology and prognosis of patients with left bundle branch block (LBBB), morphological alterations of the myocardium both resulting in and ensuing LBBB, cardiac biomechanics in LBBB, and possibilities of its correction.

Hemodynamic implications of left bundle branch block

Left bundle branch block (LBBB), traditionally viewed as an electrophysiologic abnormality, is increasingly recognized for its profound hemodynamic effects. LBBB causes asynchronous myocardial activation, which, in turn, may trigger ventricular remodeling. Exercise nuclear studies frequently show reversible perfusion defects in the absence of obstructive coronary artery disease and some patients with intermittent LBBB develop angina coincident with the onset of LBBB. It is uncertain, however, if these phenomena are because of myocardial ischemia or ventricular asynergy. LBBB is associated with impaired systolic and diastolic function. In patients with dilated cardiomyopathy (DCM), LBBB is accompanied by progressive left ventricular (LV) dilatation and mitral regurgitation. It is not known whether LBBB is the cause or the consequence of LV dilatation. DCM patients with LBBB, as compared to those with normal intraventricular conduction, are more likely to have a nonischemic etiology, profound LV dilatation, lower ejection fraction, increased symptomatology, and shorter survival. Patients with DCM and acceleration-dependent LBBB may benefit from restoration of a narrow QRS complex by suppressing the heart rate with beta-blocker. There is extensive research underway in patients with DCM and LBBB to evaluate the short and long-term effects of normalization of ventricular activation sequence with high septal, LV, or biventricular pacing.

[Hemodynamic benefits of left ventricular pacing in two pacemakers syndromes with refractory heart failure]

We describe two cases in which right ventricular pacing produced severe hemodynamic deterioration and in which changing the pacing from the right to the left ventricle sharply corrected these alterations, while simultaneous biventricular pacing did not. Chronic left ventricular pacing can solve hemodynamic alterations in severe pacemaker syndromes, thereby avoiding the need for mitral prosthesis implantation in some cases. The use of this procedure today should be individualized, including acute hemodynamic and echocardiographic studies, because the width of the QRS complex during pacing is not a significant predictor of hemodynamic efficiency.

Mitral regurgitation after atrioventricular node catheter ablation for atrial fibrillation and heart failure: acute hemodynamic features

BACKGROUND

Radiofrequency catheter ablation of the atrioventricular node and pacemaker insertion have been associated with occasional development of mitral regurgitation (MR). Ventricular pacing might result in MR if (1) left ventricular (LV) compliance is decreased and/or (2) mitral valve leaflet apposition is disturbed. We studied acute hemodynamic changes resulting from initiation of ventricular pacing in patients undergoing ablation.

METHODS AND RESULTS

Thirteen patients (10 men and 3 women) with a mean age of 73.4 +/- 8. 6 years, with chronic atrial fibrillation and congestive heart failure, had permanent ventricular pacemaker insertion with lead placement at the right ventricular (RV) apex. The following hemodynamic recordings were obtained before ablation (during atrial fibrillation) and then immediately after ablation (during RV pacing): heart rate, mean arterial pressure, LV end-diastolic pressure (LVEDP), mean pulmonary capillary wedge pressure, V-wave amplitude, and cardiac index. Presence of MR was assessed by V-wave amplitude and the results of LV angiography. In patients who had MR, recordings were also obtained during temporary ventricular pacing from the RV outflow tract (RVOT). As a group there were no significant changes in any hemodynamic measurement. Before ablation, mild MR by LV angiogram was present in 5 patients, but none had large V-wave amplitude. After ablation, mild MR was present by LV angiogram in 6 patients, and in 3 of these patients large V-wave amplitude developed (mean amplitude 42.7 +/- 2.2 mm Hg; assigned to group 1). This was associated with a rise in LVEDP in 1 patient (consistent with reduced LV compliance), but LVEDP was unchanged in the other 2 patients (suggesting abnormal mitral valve leaflet apposition). All patients in group 1 exhibited a fall in V-wave amplitude when the pacing site was moved to the RVOT.

CONCLUSIONS

Both reduced LV compliance and disturbed mitral valve leaflet apposition contribute to MR after ablation. MR is reduced by pacing from the RVOT.