This study compares LV performance during high right ventricular septal (RVS) and apical (RVA) pacing in patients with LV dysfunction who underwent His-bundle ablation for chronic AF. We inserted a passive fixation pacing electrode into the RVA and an active fixation electrode in the RVS. A dual chamber, rate responsive pulse generator stimulated the RVA through the ventricular port and the RVS via the atrial port. Patients were randomized to initial RVA (VVIR) or RVS (AAIR) pacing for 2 months. The pacing site was reversed during the next 2 months. At the 2 and 4 month follow-up visit, each patient underwent a transthoracic echocardiographical study and a rest/exercise first pass radionuclide ventriculogram. We studied nine men and three women (mean age of 68 +/- 7 years) with congestive heart failure functional Class (NYHA Classification): I (3 patients), II (7 patients), and III (2 patients). The QRS duration was shorter during RVS stimulation (158 +/- 10 vs 170 +/- 11 ms, P < 0.001). Chronic capture threshold and lead impedance did not significantly differ. LV fractional shortening improved during RVS pacing (0.31 +/- 0.05 vs 0.26 +/- 0.07, P < 0.01). RVS activation increased the resting first pass LV ejection fraction (0.51 +/- 0.14 vs 0.43 +/- 0.10, P < 0.01). No significant difference was observed during RVS and RVA pacing in the exercise time (5.6 +/- 3.2 vs 5.4 +/- 3.1, P = 0.6) or the exercise first pass LV ejection fraction (0.58 +/- 0.15 vs 0.55 +/- 0.16, P = 0.2). The relative changes in QRS duration and LV ejection fraction at both pacing sites showed a significant correlation (P < 0.01). We conclude that RVS pacing produces shorter QRS duration and better chronic LV function than RVA pacing in patients with mild to moderate LV dysfunction and chronic AF after His-bundle ablation.

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We studied phasic right coronary blood flow in well trained normal dogs and dogs with pulmonic stenosis. We installed electromagnetic flow transducers and pressure tubes under anesthesia to monitor right coronary blood flow, cardiac output, central aortic blood pressure, and right ventribular pressure. In normotensive dogs, systolic flow amplitude equaled early diastolic flow levels. The ratio of systolic to diastolic flow at rest was substantially greater in the right coronary bed (36+/-1.3%) than in the left circumflex bed (13+/-3.6%). Right diastolid flow runoff, including the cove late in diastole, resembled left circumflex runoff. Blood flow to the normotensive right (37+/-1.1 ml/min 100(-1) g) and the left (35+/-1.0 ml/min(-1) g) ventricular myocardium indicated equal perfusion of both cardiac walls. Throttling of systolic flow was related directly to the right ventricular systolic pressure level in the dogs with pulmonic stenosis. Retrograde systolic flow occurred in severe right ventricular hypertension. The late diastolic runoff pattern in dogs with pulmonic stenosis appeared the same as for the normotensive dogs. We obtained systolic to diastolic flow ratios of 1/3 the value of normotensive hearts in high and severe pulmonic hypertension. Electrocardiograms and studies of pathology suggested restricted blood flow to the inner layers of the right myocardium in the dogs with severe and high right ventricular hypertension. Normotensive and hypertensive peak hyperemic flow responses were similar, except for an increased magnitude of diastolic flow, with proportionately less systolic flow in hypertensive states.

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(1) Estimation of total costs of diagnostic tests for CAD requires consideration not only of the direct cost of the test per se (eg, test fees) but also of the indirect and induced costs of management algorithms based on the test (eg, cost/delta QALY). (2) It is essential to consider the clinical history (pCAD) when selecting the clinical algorithm to make a diagnosis with the lowest cost per effect or cost per utility unit. (3) Stress PET shows the lowest cost per effect or cost per utility unit in patients with pCAD < 0.70. (4) Angiography shows the lowest cost per effect or cost per utility unit in patients with pCAD > 0.70.