RESUMEN
OBJECTIVE: Optimization of defibrillation success is important to improve efficacy and minimize post-shock sequelae. Previous work has suggested an improvement in shock success when an intracardiac shock is delivered synchronized to the upslope of a VF wave. We investigated the efficacy of transthoracic defibrillation success using a novel external biphasic defibrillator which delivers shocks synchronized to the upslope of the surface ECG. METHODS: A prospective, controlled, randomized study in a research institute laboratory of male and female pigs (54.2±1.8 kg). Ventricular fibrillation (VF) was induced in 10 anaesthetized and ventilated pigs. Shocks were delivered randomly from a biphasic defibrillator in synchronized or non-synchronized mode via self-adhesive electrode pads following 30 s of VF. Energy settings at 50, 70, 80, and 100J were randomly tested. VF amplitude, impedance, and shock outcome were recorded and analysed digitally. RESULTS: A total of 300 shocks were delivered. Synchronized shocks were delivered on the upslope of the VF wave in 99% of cases. There was no significant difference in shock success between shocks delivered in synchronized or non-synchronized modes (p=0.695). There was no significant difference in the amplitude of VF between successful and unsuccessful shocks (p=0.163). Furthermore, there was no association between shock success and transthoracic impedance. CONCLUSION: The novel defibrillator used in this study was able to consistently deliver shocks on the upslope portion of the VF wave but did not show an improvement in shock success.
RESUMEN
Pulse wave velocity (PWV) is an accepted surrogate marker of arterial stiffness and may be a useful tool for assessing cardiovascular risk in hypertensive patients. The authors sought to compare a novel polyvinylidene fluoride (PVDF) piezoelectric-based sensing device for measuring PWV in the arm with a validated SphygmoCor device (AtCor Medical, West Ryde, Australia) in normal and hypertensive patients. They also sought to compare measured PWV in the forearm (brachial-radial PWV [BRPWV]) with values obtained in the carotid-radial segment (carotid-radial PWV [CRPWV]). Under standardized conditions, CRPWV in 108 normotensive patients with both devices was measured. BRPWV was measured with the PVDF device. Identical measurements were made in a group of 82 hypertensive patients before and after optimization of blood pressure control. Mean CRPWV was 8.7 m/s in the normotensive group and 9.4 m/s in the hypertensive group. Mean BRPWV was 9.2 m/s in the normotensive group and 10.3 m/s in the hypertensive group. There was excellent correlation between the 2 devices when comparing individual CRPWV values (normotensive group, R(2) = 0.92; mean bias 0.04 m/s; hypertensive group, R(2) = 0.89, mean bias 0.08 m/s). Correlation was also favorable when measuring changes in CRPWV in hypertensive patients undergoing pharmacotherapy (PVDF -0.52 ± 0.90 m/s vs SphygmoCor -0.53 ± 1.01 m/s; R(2) = 0.81). Measured values for BRPWV were significantly higher than CRPWV values, and this discrepancy was more marked in the hypertensive group. The PVDF piezoelectric device has excellent correlation with the validated SphygmoCor device when measuring PWV. This novel device may have an important role in patients with conditions such as hypertension.
