The Importance of Different Atrioventricular Delay for Left Ventricular Filling in Sequential Pacing: Clinical Implications

We assessed the influence and clinical consequences of different AV delay on ventricular filling in 30 patients (mean age 60 ± 5 years) who had ODD pacemakers for AV block. All 30 patients presented a normal ejection fraction, but in 18 cases (Group I), an echo-Doppler examination revealed ventricular hypertrophy (mean end-diastolic wall thickness of 1.4 ± 0.16 cm. LV mass index 155 ± 17g/m²), and an abnormal relaxation pattern (isovoiumetric relaxation time = 124.72 ± 11.82; early to late peak velocity = 0.6 ± 0.03; deceleration time - 296.83 ± 34.02 ms). Group II included the remaining 12 patients who had a normal filling pattern. In all 30 patients, the pattern was reassessed following modification of the AV delay (200, 150, 100. and 75 ms). Patients at baseline (AV delay of 200 ms) also underwent an exercise test with determination of respiratory gas exchange. In Group I, 13 (72.5%) patients were classified as Weber class B (VO₂ Max 16.8 ± 1.7mL/min per kg); and 5 (27.5%) were Class A (VO₂ Max 22.5 ± 1.4 mL/min per kg). In Group II, all 12 patients were classified as Weber Class A. In Group II, changes in AV delay caused no consistent variations in filling pattern, and therefore AV delay was not modified. In Group I patients, since reduction to 100 ms resulted in normalization of the filling pattern, the AV delay was programmed to 100 ms. A graded exercise test repeated after 6 months follow-up showed an improved Weber class in 13 patients (from B to A) and greater VO₂ Max in the remaining five already in Class A. We concluded that, in sequential paced patients with normal ejection fraction but abnormal relaxation pattern, modification in AV delay can induce normalization of filling and improvement in cardiac functional capacity.