Electrophysiological and haemodynamic basis for application of new pacemaker technology in sick sinus syndrome and atrioventricular block.

Abstract

SUMMARY A fundamental description of pacemaker systems which are commercially available or in clinical validation is given as a background for their application in a series of 62 consecutive patients presenting over a period of 1 year for permanent cardiac pacing. The patients (23 (37%) sick sinus syndrome, 38 (61%) atrioventricular block, and 1 ventricular tachycardia) were studied electrophysiologically and haemodynamically to allow the appropriate application of a pacemaker system. In sick sinus syndrome, 8 patients had permanent atrial pacing, 14 ventricular pacing, and 1 atrioventricular sequential pacing; in atrioventricular block, 8 patients had atrial synchronous ventricular inhibited pacing and the remaining 30 had ventricular pacing. A high incidence of atrial fibrillation, 9 patients, and abnormal sinus node function, 15 patients, precluded wider use of atrial synchrony. The results show benefit in acute haemodynamic studies of using systems including atrial sensing and/or pacing, and with greater availability of atrioventricular sequential and still more advanced pacemakers with dual sensing as well as dual pacing the majority of patients may be offered this benefit. Permanent, implanted cardiac pacemakers have been used clinically since 1959 (Elmqvist and Senning, 1960). As is common with new treatments, the initial indications for use were very narrow, in this instance intended primarily for ventricular stimulation in cases of complete atrioventricular block with Adams-Stokes seizures. These early pacing systems maintained a constant regular cardiac rhythm by stimulating the ventricles asynchronously at a fixed rate, usually 70 pulses per minute. As a fuller understanding of cardiac pacing was realised, indications for use expanded to include management of symptomatic bradyarrhythmias, tachyarrhythmias, and restoration of optimal haemodynamics. As a result, the operational types of artificial pacemakers evolved so that there now exists an armamentarium of atrial and ventricular pacemaker systems, each appropriate to certain pathological situations within a broad range of cardiac diseases.

Hemodynamic Effects of Atrial Synchronization in Acute and Long‐Term Ventricular Pacing

“…Ten (7)(8)(9)(10)(11)(12) weeks after the implantation of a permanent pacemaker measurements at rest and during exercise were repeated. No significant change in all the basic hemodynamics oc-curred during this period (Table II).…”

“…Testing in the asynchronous mode was not possible in the 2 patients with the Medtronic SPO-069 units and in one patient with SiemensElema 625. During this investigation no complications occurred; all pacemakers are working normally after a follow-up period of 12.7 (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) months. Table I summarizes the results obtained in 76 studies of 10 patients with and without A-V synchrony at rest and at exercise.…”

Associated Conduction Disturbances in Patients with Symptomatic Sinus Node Disease

“…The detection of impaired AV conduction is also of relevance for some SND patients in whom a more advantageous hemodynamic situation is provided by atrial rather than ventricular pacing (28).…”

Physiological Pacing: Present Status and Future Developments

“…The effect of atrial contribution to ventricular stroke volume of the paced heart has been extensively studied in the experimental animaP5-18 and in man. [19][20][21][22][23][24] It could be shown that not only AV synchronization, as such, was important but the optimal timing of atrial contraction during the diastolic period as well. Measuring stroke volume beat by beat by means of impedance cardiography in patients with ventricular pacemakers implanted for complete AV block, Knapp et a1.…”