This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Sweeney, M. O. Articles by Prinzen, F. W. Search for Related Content PubMed PubMed Citation Articles by Sweeney, M. O. Articles by Prinzen, F. W. Related Collections Congestive Pacemaker Arrhythmias, clinical electrophysiology, drugs Heart failure - basic studies

Advances in Arrhythmia and Electrophysiology

Ventricular Pump Function and Pacing

Physiological and Clinical Integration

Michael O. Sweeney, MD and Frits W. Prinzen, PhD

From the Brigham and Women’s Hospital (M.O.S.), Harvard Medical School, Boston, Mass; and the Department of Physiology (F.W.P.), Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands .

Correspondence to Michael O. Sweeney, MD, Cardiac Arrhythmia Service, Brigham and Women’s Hospital, Boston, MA. E-mail mosweeney@partners.org

Key Words: bundle-branch block • cardiomyopathy • heart failure • myocardial contraction • pacing

An extract of the first 250 words of the full text is provided, because this article has no abstract.

	Introduction

 
Optimal cardiac pump function depends on ordered mechanical events that are orchestrated by electrical timing. This electromechanical coupling occurs at multiple anatomic levels: within atria, between atria and ventricles, between ventricles, and especially within the left ventricle (LV). Such disruptions to proper electrical timing result in disordered mechanical events (desynchronization, or "dyssynchrony"), can occur spontaneously or be induced in isolation or in various combinations at any level, and degrade cardiac pump function. These disruptions to normal mechanical ordering occur because of fixed or functional conduction blocks and can be generated by myocardial disease or can be induced by cardiac pacing. The adverse effects of disruption of proper electromechanical coupling at all levels with particular attention to the effects of ventricular conduction delay due to conventional (usually right ventricular apical, RVA) pacing and left bundle-branch block (LBBB) are discussed later. Subsequently, remedies for prevention or treatment are discussed along the same lines.

	Consequences of Uncoupling at Various Levels

 
Uncoupling at the Atrial Level
The right atrium and left atrium are activated nearly simultaneously (within 50 to 80 ms) during sinus rhythm. Preferential sites of interatrial conduction exist at the posterior-superior interatrial septum (Bachmann’s bundle region), fossa ovalis, and coronary sinus ostium.^1,2 Significant interatrial conduction delays (up to 200 ms or greater) can occur in myopathic atria. Similar conduction delays can be also be induced, or exacerbated, by right atrial pacing. Delayed left atrial contraction can disrupt optimal left-sided atrioventricular (AV) coupling. Severe atrial decoupling and delayed left atrial contraction reverses the left-sided AV contraction sequence, resulting in atrial transport block.³ This causes . . . [Full Text of this Article]