Diastolic dysfunction and atrial fibrillation

Abstract

Isolated diastolic heart failure (DHF) is defined as heart failure with preserved left ventricular (LV) systolic function in the absence of valve disease. DHF is a clinical diagnosis confirmed by echocardiography and is presumed to be due to diastolic dysfunction (DD). DD is characterized by abnormalities in relaxation and/or distensibility (restriction) of the left ventricle (LV). DHF accounts for 30% to 50% of patients with heart failure and is an independent predictor of atrial fibrillation (AF) in the elderly. This paper will describe the diagnosis of DD in both sinus rhythm and AF as well report on agents used in the treatment of DHF and prevention of AF in DHF. DIAGNOSIS IN SINUS RHYTHM: Early DD is identified by Doppler determined mitral inflow measurements: The ratio of the peak velocity of the early filling (E) wave to the atrial contraction (A) wave, E/A is <1, the deceleration time (DT) is slow (>240 ms), the isovolumic relaxation period (IRP) is prolonged (>110 ms). In Moderate DD, the LV stiffens with elevated left atrial pressure resulting in "pseudonormal" filling pattern with E/A ratio >1. This is unmasked by pulmonary vein measurements with the systolic forward flow (S) being less than (approximately 50%) diastolic forward flow wave (D). Retrograde flow wave (A (R)) is increased >0.25 m/s. As the LV stiffens, restrictive features develop resulting in rapid early filling with E/A ratio >2, shortened DT <150 ms and IRP <60 ms. The A (R) wave is increased in amplitude >0.35 m/s and duration >30 ms. Early diastolic filling reflected by tissue Doppler determination of mitral annulus motion velocity (E') is reduced in DD. The E/E' ratio correlates well with filling pressures. DIAGNOSIS IN AF: Atrial contraction is absent and therefore measurements independent of atrial influence such as DT, IRP, E/E' ratio and S wave are used. THERAPY FOR DHF AND AF PREVENTION: While not well established, Treatment with ACE-inhibitors, angiotensin receptor blockers (ARBs) and aldosterone antagonists have shown objective improvement in DHF and ARBs have been found to decrease the incidence of AF. Candesartan decreases the incidence of AF in patients with symptomatic heart failure and preserved LV systolic function. There are ongoing studies of Irbesartan and spironolactone to evaluate their effect on DHF treatment. Diagnosis of DD is made by echocardiography in patients with sinus rhythm or in patients with AF. Randomized controlled trials in patients with DHF are under way. The treatment of DHF and AF prevention will continue to evolve.