Biomedical subjects

Xiaozheng Zhang

Publications and source records attributed to Xiaozheng Zhang.

3 recordsLinked to original sources

PubMed2005

Serial changes in right ventricular apical pacing lead impedance predict changes in left ventricular ejection fraction and functional class in heart failure patients.

Pacing impedance has been proposed to monitor the clinical status of patients with congestive heart failure (CHF). This study examined whether changes in right ventricular (RV) pacing impedance correlate with changes in left ventricular ejection fraction (LVEF) and New York Heart Association (NYHA) functional class during long-term follow-up in pacemaker recipients with CHF. The study included 67 patients, 70 +/- 12 years of age, in NYHA class II or III, and with a mean LVEF = 29 +/- 8% at implant. LVEF, NYHA class, and bipolar pacing impedance at the RV outflow tract (RVOT) and apex (RVA) were measured at implant and at 3, 6, 9, and 12 months of follow-up. At implant, impedance was similar in RVOT (548 +/- 115 Omega) and RVA (571 +/- 174 Omega). Between implant and 3 months, mean impedance decreased (P < 0.0001) at both the RVOT (472 +/- 62 Omega) and RVA (488 +/- 86 Omega), LVEF increased (43 +/- 14%, P < 0.0001), and the NYHA class decreased from 2.4 +/- 0.5 to 2.1 +/- 0.6 (P = 0.0001). Changes in RVA impedance correlated with changes in LVEF (r = 0.45, P = 0.002). A 50 Omega decrease in RVA impedance corresponded to a 3% decrease in LVEF. RVA impedance decreased significantly as NYHA class increased from I to IV (P = 0.04). There was no correlation between impedance measured at the RVOT and LVEF or NYHA class. A decrease in bipolar pacing impedance at the RVA was associated with worsening LVEF and the NYHA class. The use of pacing impedance to monitor the clinical status in CHF is dependent on the RV pacing site.

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PubMed2003

Automatic sensor algorithms expedite pacemaker follow-ups.

OBJECTIVE: Automatic algorithms can be used to optimize settings and reduce the duration of pacemaker (PM) clinical follow-up. METHODS: This study prospectively evaluated 87 patients (74.2 +/- 10.7 years old, 52% men) who received PM with the Autoslope algorithm. Patients randomized to the manual group (group M, n = 43) performed a walk test and used sensor-indicated rate histograms to adjust the sensor, while in the automatic group (group A, n = 44) the sensor was automatically adjusted by the Autoslope. The patients were followed for 6 months. Follow-up time required for device interrogation and optimal sensor set-up, and the number of sensor parameters reprogramming were recorded. Changes in the patients' activity level were also evaluated. RESULTS: Group A required significantly less follow-up time than group M (9.4 +/- 5.7 min vs 13.5 +/- 8.5 min, P = 0.0002). The average number of sensor parameters reprogrammed during visits was significantly lower in group A than M (0.6 +/- 0.9 vs 0.9 +/- 1.3, P = 0.048). Threshold was adjusted 34.4% of the time in the sensor evaluations in group M versus 12.9% in group A (P = 0.0004). Although more patients in group A reported being more active, the changes in patients' activity level did not lead to increasing sensor setup time or number of parameter reprogramming in either group. CONCLUSIONS: Auto sensor adjustment required less time during routine PM clinical follow-up by reducing steps needed for manual sensor threshold adjustment.

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PubMed2003

Right ventricular outflow versus apical pacing in pacemaker patients with congestive heart failure and atrial fibrillation.

INTRODUCTION: Prior studies suggest that right ventricular apical (RVA) pacing has deleterious effects. Whether the right ventricular outflow tract (RVOT) is a more optimal site for permanent pacing in patients with congestive heart failure (CHF) has not been established. METHODS AND RESULTS: We conducted a randomized, cross-over trial to determine whether quality of life (QOL) is better after 3 months of RVOT than RVA pacing in 103 pacemaker recipients with CHF, left ventricular (LV) systolic dysfunction (LV ejection fraction < or = 40%), and chronic atrial fibrillation (AF). An additional aim was to compare dual-site (RVOT + RVA, 31-ms delay) with single-site RVA and RVOT pacing. QRS duration was shorter during RVOT (167 +/- 45 ms) and dual-site (149 +/- 19 ms) than RVA pacing (180 +/- 58 ms, P < 0.0001). At 6 months, the RVOT group had higher (P = 0.01) role-emotional QOL subscale scores than the RVA group. At 9 months, there were no significant differences in QOL scores between RVOT and RVA groups. Comparing RVOT to RVA pacing within the same patient, mental health subscale scores were better (P = 0.03) during RVOT pacing. After 9 months of follow-up, LVEF was higher (P = 0.04) in those assigned to RVA rather than RVOT pacing between months 6 and 9. After 3 months of dual-site RV pacing, physical functioning was worse (P = 0.04) than during RVA pacing, mental health was worse (P = 0.02) than during RVOT pacing, and New York Heart Association (NYHA) functional class was slightly better (P = 0.03) than during RVOT pacing. There were no other significant differences between RVA, RVOT and dual-site RV pacing in QOL scores, NYHA class, distance walked in 6 minutes, LV ejection fraction, or mitral regurgitation. CONCLUSION: In patients with CHF, LV dysfunction, and chronic AF, RVOT and dual-site RV pacing shorten QRS duration but after 3 months do not consistently improve QOL or other clinical outcomes compared with RVA pacing.

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