A four-week study conducted on animals revealed that regulating ventricular rates and heart structure in models with irregular heart rhythms can inhibit chronic heart failure (CHF).
According to the study, published in the Journal of Cardiovascular Electrophysiology, thirteen goats were subjected to rapid atrioventricular (AV) pacing with high atrial and ventricular rates (240 beats/min) while an additional five goats were subjected to a high atrial rate (240 beats/min) and low, regular ventricular rate (80 beats/min). Six of the 13 goats in the first group died suddenly after developing signs of end-stage CHF. No goats died from the group with the low ventricular rate.
"The results of this experimental research demonstrate that the changes in atrial function and structure that evolve during a chronic atrial tachyarrhythmia do not relate to the high atrial rate itself but rather to the concurrent high ventricular rate and the consequent development of heart failure," states lead researcher, Bas A. Schoonderwoerd, MD, PhD.
Changes in atrial function and structure are known as atrial remodeling. Schoonderwoerd explains that this remodeling can make it more difficult to regain normal heart rhythms; remodeling can even be induced by heart failure itself. The high pressure and irregular pumping caused by the high rates used in the first group of goats are similar to the rapid rates of atrial fibrillation and can cause the heart ventricles to wear out.
"This may imply that in patients with atrial fibrillation, we must aim at keeping the ventricular rate low [with drugs] and thus prevent the development or inhibit the progression of heart failure," adds Schoonderwoerd.
Increased levels of atrial natriuretic peptides (ANP), a cardiac hormone that regulates blood pressure, are also noted in this experiment. The researchers conclude that "a rise in atrial rate results in an additional increase of circulating ANP, but only in the presence of elevated atrial pressures." ANP levels also rise with atrial pressure, independent of atrial rate. CHF developed in the animals of the experiment that showed sustained ANP release and high ventricular rates.
More research is needed to support this evidence in human models due to interspecies differences and because arrhythmia and/or heart failure is usually present in a clinical situation for many months.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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