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Atrioventricular (AV) delay optimization in sequential and biventricular (BiV) pacing, although widely recommended, is often poorly performed in clinical practice as an improper setting can reduce the success of the stimulation. Despite the several methods proposed, the AV delay is frequently programmed in an empirical way or left to a predefined value (usually the manufacturer's setting), without considering the different variables involved in this context, concerning the intra- and interindividual variability of the electromechanical events, the peculiarities of the several cardiopathies, the spontaneous interatrial and AV conduction, the pharmacological therapy, and the pacing mode. The manuscript illustrates the physiological bases of the optimization, describes why and how to programme the best AV delay at rest and during daily activities and discusses critically all methods proposed, divided into three groups: predefined formulas, iterative attempts, and automatic settings. The manuscript is not only a review because it tries to clarify this complex topic, stating the fundamental concept in BiV pacing; the optimal AV delay should be short enough to have always a pre-exitated stimulation and contemporary an optimal left ventricular filling. The paper suggests new purposes and new solutions for this goal, it shows the limits of the actual guidelines and the disappointing results obtained in several studies by automatic methods, goading to find new algorithms.

Twenty-three patients affected by severe, refractory angina were submitted to permanent spinal cord stimulation (SCS) and then followed in our outpatient clinic for 24 months. During the follow-up period, the number of weekly angina episodes drastically dropped from 9.2 (preimplant) to 1.8 in the 3rd, 2.5 in the 6th, 4.5 in the 12th, and 4.2 in the 24th month, with a statistically significant difference (P < 0.01) between the first and last values. A significant increase in the average exercise time from 320 +/- 120 seconds (in baseline condition) to 410 +/- 115 seconds (during SCS) was observed at the treadmill stress test (P < 0.01). SCS was well tolerated by all the patients. However, 7 patients died during follow-up (3 myocardial infarctions, 2 noncardiac deaths, and 2 sudden deaths). Three generators were replaced because of battery depletion after 15, 17, and 21 months. No serious complication was observed. In conclusion, in patients with otherwise intractable angina or already submitted to myocardial revascularization, SCS is very effective in reducing the number of angina episodes. The time of the work during exercise stress test is also significantly prolonged.

According to our data, in VDD single-lead systems the amplitude of the atrial signal is stable over time in every physical activity. High RAD and low RAVD values may select patients with poor atrial sensing stability. Anyway, taking into account that no atrial oversensing was observed, atrial sensitivity setting at the highest value should be recommended.