Respiratory changes in vasovagal syncope.

INTRODUCTION: Respiratory changes accompany the cardiovascular changes during head-up, tilt test-induced vasovagal syncope. METHODS AND RESULTS: Using the 45-minute 60 degrees head-up Westminster protocol, 29 patients were studied (mean age 53.9+/-20.0 years; 19 females). Two groups resulted: tilt-induced vasovagal syncope positive and negative. The cardiorespiratory parameters blood pressure (BP), heart rate (HR), tidal volume, and minute volume were measured. Comparisons of the cardiorespiratory parameters were made within the positive group and negative group, and then between the two groups. There were 14 in the positive group and 15 in the negative group. Baseline measurements were normalized to 1.0. Comparing the late tilt periods between the positive and negative groups, there were differences in BP (P < 0.002), HR (P < 0.002), tidal volume (P < 0.05), and minute volume (P < 0.002). In the positive group comparing early with late intervals: BP 1.11+/-0.09 versus 0.49+/-0.17, P < 0.0001; HR 1.18+/-0.12 versus 0.85+/-0.35, P < 0.009; tidal volume 1.39+/-0.34 versus 2.17+/-1.00, P < 0.015; and minute volume 1.24+/-0.26 versus 3.3+/-2.03, P < 0.0025. There were no comparable cardiorespiratory changes in the negative group. CONCLUSION: There were significant differences in the respiratory and cardiovascular parameters measured between those who were positive and those who were negative for tilt-induced vasovagal syncope. Within the positive group, in addition to the falls in HR and BP, there were significant increases in minute volume and tidal volume during late tilt. This suggests that there may be a role for respiratory sensors in vasovagal syncope that may permit earlier and hence possibly more effective therapy for selected patients.

Determining the optimal pacing intervention rate for vasovagal syncope.

INTRODUCTION: In this study, patients with rate hysteresis pacemakers implanted for vasovagal syncope were re-studied using serial tilt testing to determine whether, once triggered, pacing was more effective if the intervention rate was higher than the standard rate. METHODS AND RESULTS: Twenty patients (mean age 55.4 years, range 23-81, 14 male) were studied, with randomisation to either initial standard rate (80-90 beats/min) intervention, or to initial high rate (120 beats/min) intervention. Although 18 of the 20 reported complete abolition of syncope since pacing, only 8 patients could be objectively assessed. The respective mean time to tilt down after symptom onset with standard and high rate intervention was 193+/-234s and 185+/-143s, (P>0.05). CONCLUSION: Repeat tilt testing was only of limited value in assessing the benefit of pacing. There was no advantage with high rate intervention in delaying the loss of consciousness (or intolerable symptoms) after the initial onset of symptoms.

Mode switching for atrial tachyarrhythmias.

Mode switching for atrial tachyarrhythmias is a concept that originated from use of DDI mode and was introduced in the early 1990s to prevent dual-chamber pacemakers from ventricular tracking of rapid atrial rates. This article describes the currently available systems and discusses the advantages and disadvantages of the technique. The results of a preliminary randomized controlled trial of 1 algorithm and plans for a second study are presented.