Patient with sick sinus syndrome and implanted dual-chamber pacemaker with reduced P-wave duration following low interatrial septal pacing: Case report.

INTRODUCTION: A dual-chamber pacemaker (DDD/R) for a sinus node disease is sometimes referred to as a physiological pacemaker as it maintains atrioventricular synchrony, however several clinical trials have proved its inferiority to a nonphysiological single-chamber ventricular back-up pacing. PATIENT CONCERNS: A subject of the study is a 74-year-old woman with a sick sinus syndrome (SSS) and a previously implanted physiological DDD/R pacemaker. The SSS was diagnosed because of patient's very slow sinus rhythm of about 36 bpm, and due to several episodes of dizziness. After the DDD/R implantation the percentage of atrial pacing approached 100%, with almost none ventricular pacing. DIAGNOSES: Sick sinus syndrome, complete Bachmann's bundle block, atrial fibrillation, atrial flutter. INTERVENTIONS: The patient was previously implanted with a physiological DDD/R pacemaker. Several years after the implantation, the atrial fibrillation was diagnosed and the pulmonary vein isolation was then performed by cryoablation. During the follow-up after pulmonary vein isolation, the improvement of mitral filling parameters was assessed using echocardiography. Shortly thereafter the patient developed the persistent paroxysm of a typical atrial flutter which was successfully terminated using a radiofrequency ablation. No recurrence thereof has been observed ever since (24 months). OUTCOMES: The atrial electrode of the pacing system was implanted within the low interatrial septal region that resulted in a reduced P-wave duration compared to native sinus rhythm P-waves. The said morphology was deformed because of the complete Bachmann bundle block. That approach, despite a nonphysiological direction of an atrial activation, yielded relatively short P-waves (paced P-wave: 179 ms vs intrinsic sinus P-wave: 237 ms). It also contributed to a significantly shorter PR interval (paced PR: 204 ms vs sinus rhythm PR: 254 ms). CONCLUSIONS: The authors took into consideration different aspects of alternative right atrial pacing sites. This report has shown that in some patients with a sinus node disease, low interatrial septal pacing can reduce the P-wave duration but does not prevent from the development of atrial arrhythmias.

The true nature of P wave dispersion.

BACKGROUND: The electrophysiological activity of the heart is recorded and presented in form of electrocardiography (ECG). In 1998, the concept of P wave dispersion as the risk factor for atrial fibrillation (AF) recurrence was introduced. It was calculated as the difference between the longest and the shortest P wave. OBJECTIVES: To prove that the P wave dispersion is an artifact of low accuracy in P wave measurement. MATERIAL AND METHODS: The study included 104 patients (48 women, 56 men), aged 63 ±14 years, undergoing various electrophysiological procedures. The P wave was measured twice - firstly at the paper speed of 50 mm/s, enhancement ×8 (standard - imprecise), and secondly at 200 mm/s, ×64-256 (precise). RESULTS: The imprecise measurement method resulted in different duration of all P wave parameters in comparison with precise measurement. The longest P wave duration (Pmax) measured imprecisely was 105.1 ±22.1, the Pmax measured precisely was 134.0 ±21.3 (p < 0.001). The P dispersion measured imprecisely was 44.1 ±16.8 and the P dispersion measured precisely was 2.8 ±3.4 (p < 0.0001). The correlation between imprecise Pmax and imprecise Pmin was r = 0.664 (p < 0.05). The correlation between imprecise Pmax and imprecise P wave dispersion was r = 0.612 (p < 0.05). The correlation between precise Pmax and Pmin was almost 1.0 (r = 0.987, p < 0.05). CONCLUSIONS: The P wave dispersion does not exist. The measurements of the P wave have to be precise to assure the highest scientific and medical sincerity. The highest clinical value is related to the P wave duration.