Atrioventricular synchrony

A decision to refer for permanent pacemaker implantation for loss of atrioventricular synchrony due to first degree AV nodal block is challenging. In the setting of normal conduction in the ventricles, the improvement that may be gained by improving atrioventricular synchrony must be weighed against... 

Sassone B, De Simone N, Parlangeli G, Tortorici R, Biancoli S, Di Pasquale G. Pacemaker-induced mitral regurgitation prominent role of abnormal ventricular activation sequence versus altered atrioventricular synchrony. Ital. Heart J. 2001 2 441-8. 

Sparks PB, Mond HG, Vohra JK, Yapanis AG, Grigg LE, Kalman JM. Mechanical remodeling of the left atrium after loss of atrioventricular synchrony. A long-term study in humans. Circulation. 1999 100 1714-1721. 

Fig. 18.15 Posteroanteiior (i4) and lateral (B) chest radiographs of a dual-chamber pacing system. The atrial lead is positioned in a septal position (arrow). This patient had extremely long intra-atrial conduction times, and septal placement was the only way to maintain effective atrioventricular synchrony.

Symptom-targeted therapy includes decreasing pulmonary venous pressure, maintaining atrial contraction and atrioventricular (AV) synchrony, and reducing heart rate. Exercise tolerance is increased by reducing exercise-induced increases in blood pressure and heart rate. 

An important step in symptom-targeted therapy that acts to decrease pulmonary venous pressures is to maintain atrial contraction and atrioventricular (AV) synchrony. Maintaining atrial contraction and AV synchrony is important both in preserving normal cardiac output and in keeping LV diastolic pressure low. Chemical or electrical cardioversion of persistent atrial tachyarrhythmias will decrease diastolic pressure, increase cardiac output, and resolve pulmonary edema. An AV sequential pacemaker should be used to treat bradyarrhythmias in patients requiring pacing. 

A dual chamber pacemaker (with one lead In the atrium and another in the ventricle) provides versatile programming functions and can sense and pace In both the atrium and ventricle. This type of pacemaker mimics the normal cardiac cycle and maintains atrioventricular (AV) synchrony. It may be used for patients with chronic or intermittent AV block and for those who need atrial pacing or have delayed AV conduction or an increased risk of heart block. 

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