Biomedical subjects

Zaffer A Syed

Publications and source records attributed to Zaffer A Syed.

4 recordsLinked to original sources

PubMed2005

Rhythm classification by correlation-waveform morphology analysis of atrial and ventricular electrogram signals.

We tested the use of correlation-waveform analysis (CWA) of atrial and ventricular electrograms (EGMs) to distinguish ventricular tachycardia (VT) from supraventricular tachycardia (SVT). Patients undergoing electrophysiologic testing were enrolled. EGMs recorded during induced tachycardias were compared with EGMs recorded during sinus and paced rhythms, taken as templates, by assigning a CWA percent-match (CPM) score. Twenty-two patients were studied: 15 men and 7 women (mean age 48 years); 16 with SVT and 6 with VT. Using a sinus-rhythm template, the atrial CPM scores for SVT and VT were 66%+/- 20% and 93%+/- 5%, respectively (P = 0.0034). With a CPM-score cutoff of 85%, the sensitivity for correctly identifying VT was 100% and the specificity for rejection of SVT was 80%. The corresponding ventricular-CPM scores for SVT and VT were 81%+/- 12% and 72%+/- 24%, respectively (P = 0.13, cutoff = 65%, sensitivity = 50%, and specificity = 90%). Using a ventricular template with atrial pacing, the ventricular-CPM scores for SVT and VT were 87%+/- 9% and 76%+/- 14%, respectively (P = 0.028, cutoff = 70%, sensitivity = 50%, and specificity = 93%). Atrial CWA matching is superior to ventricular CWA matching in discriminating between SVT and VT. CWA matching in both chambers could potentially achieve better discrimination.

Atrial Function↗

PubMed2005

Effect of short pulse width programming in AutoCapture devices.

Pacing chronaxie can increase over time. The impact of a short pulse duration on threshold (THR) variations, frequency of noncapture episodes, and overall patient safety has not been fully studied. AutoCapture (AC) pacemakers are capable of memorizing THR trends and loss of capture (LOC) episodes. The study included 20 recipients of AC pacemakers (mean age = 76 +/- 9 years, 15 men) followed for 6 months. They were randomly assigned to pulse durations of 0.2 versus 1.0 ms at 1 month, and crossed over to the alternate programming at 3 months. Evoked response (ER) and AC tests were performed at follow-up. At 0.2 ms and 1.0 ms, the mean number of LOC/day was 2.37 +/- 5.81 and 0.91 +/- 0.49, respectively (ns). LOC trends between follow-up were significantly different with 0.2 versus 1.0 ms pulse duration (P < 0.01). AC THR at 1.0 ms was significantly lower (0.44 +/- 0.77) than at 2.0 ms (0.97 +/- 0.26, P < 0.05). No patient reported symptoms related to LOC during the study. Pulse duration programmed near the strength-duration curve is associated with greater variations in THR and LOC. AC responds to these changes by delivering 4.5 V pulses and keeping the capture THR at low, though safe values.

Aged↗

PubMed2005

AutoCapture with dual-coil leads of implantable cardioverter defibrillator.

AutoCapture (AC) can confirm ventricular capture with true bipolar single coil leads of implantable cardioverter defibrillators (ICD). The compatibility of AC with a new, true bipolar, dual-coil ICD lead needed to be evaluated. This multicenter study enrolled 46 patients (69 +/- 10 years, 37 men) undergoing ICD implantation. All patients received a true bipolar, dual-coil lead. Evoked response (ER) sensitivity and AC threshold tests were performed using a pulse generator with the AC algorithm. Mean capture threshold was 0.85 +/- 0.67 V, pacing impedance 612 +/- 225 Omega, R wave amplitude 13.85 +/- 6.17 mV, and defibrillation threshold 14.4 +/- 5.1 J. AC was recommended in 45 patients (97.8%) with ER and polarization values of 14.86 +/- 7.32 mV and 0.87 +/- 0.69 mV, respectively. The AC algorithm was highly compatible with true bipolar, dual-coil ICD leads. An AC algorithm specifically designed for an ICD may improve the generator longevity. Further examination of AC compatibility with other leads is warranted.

Aged↗

PubMed2003

Use of the AutoCapture Pacing System with implantable defibrillator leads.

INTRODUCTION: Previous studies using various bipolar pacemaker leads have shown that the AutoCapture (AC) Pacing System is able to verify ventricular capture and regulate pacing output, increasing patient safety with respect to unexpected threshold changes and potentially prolonging device longevity. An increasing number of patients with implantable cardioverter defibrillators (ICDs) require ventricular pacing that contributes to a shortening of longevity of these systems. This prospective study tested the compatibility of the AC system with bipolar ICD leads. METHODS: The AC algorithm was evaluated prior to ICD testing in 30 ICD recipients. A single coil, active fixation, true bipolar ventricular lead was implanted in 21 patients, and a dual coil, passive fixation, integrated bipolar ventricular lead was implanted in 9 patients. A ventricular evoked response sensitivity test and an AC threshold test were performed using a pacemaker with the ventricular AC algorithm. RESULTS: AC was recommended in 22/30 (73.3%) of implants, including 20/21 (95.2%) with the single coil and 2/9 (22.2%) with the dual coil lead. Mean polarization was lower (1.23 +/- 0.95 mV vs 3.70 +/- 2.33 mV, P = 0.013) while the mean evoked response was higher (18.04 +/- 8.29 mV vs 10.13 +/- 4.22 mV, P = 0.002) with the single coil leads. CONCLUSION: Automatic threshold tracking using the AC is compatible with ICD leads. Leads with lower polarization and greater evoked response are more likely to result in recommendation of AC use. Use of this system offers the potential for increasing ICD generator longevity and improving patient safety in response to late unexpected threshold increases.

Aged↗