Long-Term Outcome of Single-Chamber Atrial Pacing Compared with Dual-Chamber Pacing in Patients with Sinus-Node Dysfunction and Intact Atrioventricular Node Conduction

PURPOSE: The optimal pacing mode with either single chamber atrial pacemaker (AAI or AAIR) or dual chamber pacemaker (DDD or DDDR) is still not clear in sinus-node dysfunction (SND) and intact atrioventricular (AV) conduction. MATERIALS AND METHODS: Patients who were implanted with permanent pacemaker using AAI(R) (n = 73) or DDD(R) (n = 113) were compared. RESULTS: The baseline characteristics were comparable between the two groups, with a mean follow-up duration of 69 months. The incidence of death did not show statistical difference. However, the incidence of hospitalization for congestive heart failure (CHF) was significantly lower in the AAI(R) group (0%) than the DDD(R) group (8.8%, p = 0.03). Also, atrial fibrillation (AF) was found in 2.8% in the AAI(R) group, which was statistically different from 15.2% of patients in the DDD(R) group (p = 0.01). Four patients (5.5%) with AAI(R) developed AV block, and subsequently switched to DDD(R) pacing. The risk of AF was lower in the patients implanted with AAI(R) than those with DDD(R) [hazard ratio (HR), 0.84; 95% confidence interval, 0.72 to 0.97, p = 0.02]. CONCLUSION: In patients with SND and intact AV conduction, AAI(R) pacing can achieve a better clinical outcome in terms of occurrence of CHF and AF than DDD(R) pacing. These findings support AAI(R) pacing as the preferred pacing mode in patients with SND and intact AV conduction.

The Effect of Cryoinjury on Ventricular Tachycardia in the Swine Right Ventricle

This study was performed to assess the influence of the cryoinjury on the dynamics of wavefronts and to determine whether they can convert ventricular fibrillation (VF) to ventricular tachycardia (VT) in fibrillating right ventricular (RV) of swines using an optical mapping system. A cryoinjury with a diameter of 12 mm was created on the epicardium of perfused RV of swines (n = 6) and optical mapping were taken from baseline until 10 minutes after the cryoinjury. Out of 35 cryoinjuries, the images were possible to be interpreted in 32. The optical action potential could not be observed in either the cryoinjury or peri-injury sites at 1 and 3 minutes, was observed in only the cryoinjury site at 5 minutes, and recovered in both sites at 10 minutes. The cycle length of the tachycardia was 135.9 +/- 23.6 msec at baseline, 176.2 +/- 79.3 msec at 1 minute, 187.6 +/- 97.9 msec at 3 minutes, 185.5 19.2 msec at 5 minutes, and 152.1 +/- 64.1 msec at 10 minutes. The cycle lengths at 1, 3, and 5 minutes after the cryoinjury were significantly more prolonged than that at baseline (p = 0.001, p = 0.006, p = 0.016). After the cryoinjury, the VF changed to VT in 9 (28.0%), and terminated in 2 (6.3%). These changes were observed mainly within 5 minutes after cryoinjury. The cryoinjury had anti-fibrillatory effects on the tissue with VF. This phenomenon was related to a decreasing mass and stabilizing wavefronts.

Repositioning of Pacemaker Generator due to Therapeutic Radiation: A Tunneling Method

Therapeutic ionizing radiation can damage the permanent pacemaker. Reimplantation of pacemaker should be considered when the pacemaker site is included in the radiation field. We report a case of successful repositioning of preexisting pacemaker generator and leads with subcutaneous tunneling method across the sternum instead of insertion of new leads in a female patient with breast cancer who had DDD pacemaker.

Assessment of Left Ventricular Diastolic Pressures with Pulmonary Venous Flow and Transmitral Inflow by Doppler Echocardiography

BACKGROUND: Doppler variable of mitral inflow have been used to assess left ventricular siastolic function indirectly. Pulmonary venous flow(PVF) variables could supplement mitral inflow in the estimation of left ventricular diastolic function. The purpose of this study are to assess the feasibility of PVF measurement by using transthoracic pulsed wave Doppler echocardiogram and to estimate the LV end-diastolic pressure with PVF parameters. METHODS: Fifty six patients underwent transthoracic pulsed wave Doppler echocardiagraphy (HP Sonos 1500) within 2 hours before left heart catheterization for the measurement of left ventricular pressure. RESULTS: 1) Measurement of transthoracic PVF was feasible in 50 patients(89.3%). 2) The difference between the duration of pulmonary venous reversal flow and mitral A wave(D difference, delta D) was strongly correlated with left ventricular end diastolic pressure(r=0.73, p or =12mmHg(sensitivity 90.6%, specificity 50.0%). CONCLUSION: PVF could be assessed with transthoracic Doppler ultrasound with good feasibility. PVF may be an important parameter in the evaluation of left ventricular diastolic function. PVF reveral duration exceeding that of mitral A wave would be a marker of elevated left ventricular end diastolic pressure(> or =12mmHg). Plumonary venous flow . Transmitral inflow . Left ventricular end diastolic pressure. Transthorasic doppler echocardiography.