Evaluation of acute dual-chamber pacing with a range of atrioventricular delays on cardiac performance in refractory heart failure.

OBJECTIVES: This study evaluated how variations in atrioventricular (AV) delay affect hemodynamic function in patients with refractory heart failure being supported with intravenous inotropic and intravenous or oral inodilating agents. BACKGROUND: Although preliminary data have suggested that dual-chamber pacing with short AV delays may improve cardiac function in patients with heart failure, detailed Doppler and invasive hemodynamic assessment of patients with refractory New York Heart Association class IV heart failure has not been performed. METHODS: Nine patients with functional class IV clinical heart failure had Doppler assessment of transvalvular flow and right heart catheterization performed during pacing at AV delays of 200, 150, 100 and 50 to 75 ms. RESULTS: Systemic arterial, pulmonary artery, right atrial and pulmonary capillary wedge pressures, cardiac index, systemic and pulmonary vascular resistances, stroke volume index, left ventricular stroke work index (SWI) and arteriovenous oxygen content difference demonstrated no significant changes during dual-chamber pacing with AV delays of 200 to 50 to 75 ms. There were also no changes in the Doppler echocardiographic indexes of systolic or diastolic ventricular function. The study was designed with SWI as the outcome variable. Assuming a clinically significant change in the SWI of 5 g/min per m2, a type I error of 0.05 and the observed standard deviation from our study, the observed power of our study is 85% (type II error of 15%). CONCLUSIONS: Changes in AV delay between 200 and 50 ms during dual-chamber pacing do not significantly affect acute central hemodynamic data, including cardiac output and systolic or diastolic ventricular function in patients with severe refractory heart failure due to dilated cardiomyopathy.

Adenosine-induced coronary vasodilation during transesophageal Doppler echocardiography. Rapid and safe measurement of coronary flow reserve ratio can predict significant left anterior descending coronary stenosis.

BACKGROUND: Less invasive methods are replacing traditional invasive means of measuring coronary flow reserve (CFR). Transesophageal echocardiography (TEE) is becoming a useful tool for evaluation of coronary artery disease and has recently been used to measure CFR. This has always been done using dipyridamole, but adenosine has a greater vasodilator potency and more favorable kinetics than dipyridamole. This study was done to evaluate the hypothesis that adenosine is safe, rapid, and accurate in measuring coronary blood flow reserve by TEE Doppler. METHODS AND RESULTS: Forty-nine patients who had recently undergone angiography had a transesophageal echocardiogram with visualization of the coronary arteries and measurement of blood flow velocity in the left anterior descending coronary artery (LAD) during adenosine infusion of 0.14 mg/kg per minute. Angiograms were analyzed by quantitative coronary angiography, and significant stenosis was defined as > 70% lumenal diameter narrowing. Thirty-nine of the 49 patients did not have a significant LAD stenosis (group 1); the remainder had significant disease (group 2). Good spectral Doppler recordings of blood flow velocity in the LAD were obtained in 41 of 46 patients (89%). There were no significant differences in baseline coronary blood flow velocities between the two groups. Hyperemic to baseline flow ratios were significantly higher in patients without significant LAD stenosis for peak (2.83 +/- 1.04 versus 1.78 +/- 0.36) and mean (2.68 +/- 0.96 versus 1.75 +/- 0.39) diastolic velocity. A CFR ratio > 2.1 had a sensitivity of 86%, a specificity of 79%, a positive predictive value of 46%, and a negative predictive value of 96% for the absence of critical LAD stenosis. The infusion was well tolerated. It had to be prematurely terminated in only 3 patients (6.5%), and they were asymptomatic. No patient experienced chest pain, palpitations, or flushing. Intraobserver and interobserver variabilities were low, and reproducibility of data was good (< 4%). CONCLUSIONS: Adenosine Doppler TEE is an effective, rapid, safe, and superior means of measuring CFR ratio. This method is convenient for serial measurements of CFR as well as in clinical settings such as evaluation of syndrome X, cardiomyopathy, and aortic regurgitation.