PURPOSE: The ventriculophasic response (VR) refers to shortening of atrial cycle length (PP-interval) during heart block that occurs when a QRS complex is interposed between P-waves. Sinus arrhythmia (SA) refers to shortening of atrial cycle length during respiration. We sought to determine whether SA influences VR in elderly patients with complete heart block (CHB).
METHODS: We studied 24 patients [mean age = 83±8 years] who had chronically implanted pacemakers for CHB. Coronary artery disease was present in 13 (54%), diabetes in 16(67%); 11 (46%) were on beta-blockers. During routine clinic visits, pacers were temporarily programmed to VVI mode at 30 ppm as ECG and intracardiac electrograms were recorded at 50 mm/sec paper speed to accurately measure PP-intervals. Ten seconds after the beginning of the recording patients were asked to perform 3 cycles of deep inhalation and exhalation. The VR was measured before, during and after the deep breathing.
RESULTS: VR was present in 8 (33.3%) patients at baseline and was maintained in all during deep breathing cycle. Among the 16 in whom VR was initially absent at baseline, it was observed in 9 (56.2%) during deep breathing (p=0.008). The PP-intervals containing a QRS complex during deep breathing (838.7±202.6 msec) were shorter than those in the first 10 seconds of the tracing (916.6±274,7msec) and than those at the end of the tracing (865.5±233,8 msec; p=0.006).
CONCLUSION: The SA of deep breathing enhances or amplifies the VR seen during quiet breathing. This may reflect recruitment of vagal tone by deep respiration.
CLINICAL IMPLICATIONS: Preservation of VR in the absence or presence of SA may provide insight into the autonomic function of elderly subjects with pacemakers, which may, in turn, have implications regarding underlying cardiac function and prognosis.
DISCLOSURE: Razvan Dadu, No Financial Disclosure Information; No Product/Research Disclosure Information