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Dual-chamber, rate-drop responsive cardiac pacing reduced the risk of syncope among patients with severe recurrent vasovagal syncope
TR E AT MEN T
Dual-chamber, rate-drop responsive cardiac pacing reduced the risk of syncope among patients with severe recurrent vasovagal syncope Connolly SJ, Sheldon R, Roberts RS, Gent M, on behalf of the Vasovagal Pacemaker Study Investigators. The North American Vasovagal Pacemaker Study (VPS). A randomized trial of permanent cardiac pacing for the prevention of vasovagal syncope. J Am Coll Cardiol 1999;33:16d20
OBJECTIVE To evaluate the effect of permanent dual-chamber cardiac pacing on the risk of syncope among patients with severe recurrent vasovagal syncope.
MAIN OUTCOME MEASURES The primary end-point was the first recurrence of syncope beyond 7 days post-randomization to allow time for the pacemaker group to receive their pacemakers.
DESIGN Multicenter, randomized, controlled clinical trial.
MAIN RESULTS The study was terminated at the first planned interim analysis when a large treatment effect was found which satisfied the pre-specified stopping criteria. The mean time to receiving a pacemaker was 6.7 days (range 1–22 days). There was a significantly lower rate of recurrent syncope in the pacemaker group compared with the control group (22 vs 70%; RRR 85.4%; 95% CI 59.7–94.7%; P"0.000022). The mean times to syncope were 112 and 54 days in the pacemaker and control groups, respectively. During the initial 7 days post-randomization, no patients in the pacemaker group and 6 of 27 patients in the control group experienced syncope. At least one pre-syncopal spell was reported by 63 and 74% of patients in the pacemaker and control groups, respectively. The mean rates of pre-syncopal spells were 4.5 and 10.0 per 100 days in the pacemaker and control groups, respectively.
SETTING Clinical centers in Canada and the USA. PATIENTS 54 of the planned 284 patients with at least six lifetime syncopal spells, and a positive tilt-table test with syncope or presyncope and with relative bradycardia. The mean age was 43 years (46 years in the pacemaker group and 40 years in the control group). Nearly three-quarters were females (70% in pacemaker group and 74% in control group). Patients were excluded if other causes were responsible for loss of consciousness (e.g. ventricular tachycardia, complete heart block, postural hypotension, hypersensitive carotid sinus syndrome or seizures). The median (interquartile range) number of lifetime syncopal spells was 14 (8–35) in the pacemaker group vs 35 (20–100) in the control group. INTERVENTION Patients were randomly allocated to receive either a dual-chamber pacemaker with rate-drop response (minimum rate of 60 beats/minute), or no pacemaker.
Commentary This well-designed study presents the first evidence from a randomized trial that dual-chamber pacing may benefit patients with neurocardiogenic syncope. Neurocardiogenic or vasovagal syncope is common, usually self-limiting and often responds to conservative measures. Occasionally, however, disabling symptoms persist despite conservative and medical therapies. Previous experience with single-chamber VVI pacing has been uniformly disappointing. Non-randomized studies had suggested a benefit of dual-chamber pacing, but this is the first study to use a randomized design. This study was terminated early due to a large treatment effect. As such, the study group is small and there are important differences between the study groups that could have influenced the results. Also, the study was not blinded, with the control group not receiving a pacemaker. With the natural history of neurocardiogenic syncope being so variable, a placebo effect could not be entirely excluded. The pacing group had no decrease in ‘presyncope’, however, strongly supporting the conclusion that pacing was the factor that resulted in the reduction in syncope recurrences. What cannot be determined from this study is whether it was dual chamber pacing itself or the ‘rate-drop’ feature used in this study which provided the treatment effect. These limitations will be addressed in a subsequent study. The patients included were highly selected, with very frequent episodes of syncope and with relative bradycardia on tilt-table testing.
^ 1999 Harcourt Brace & Co. Ltd
CONCLUSION Permanent, dual-chamber, rate-drop responsive cardiac pacing reduced the risk of syncope among patients with severe recurrent vasovagal syncope and a relative bradycardia on tilt-table testing.
Furthermore, it is not clear if patients considered for the study had failed all medical therapy prior to study entry. The results, thus, may not be applicable to the majority of patients with neurocardiogenic syncope. The study results do provide new and exciting evidence that dual-chamber pacing with a rate-drop response may substantially benefit some patients with highly symptomatic neurocardiogenic syncope. The results will be verified in a further study. Until then, it would seem prudent to consider such pacing therapy in selected patients when other therapies have failed to relieve frequent or disabling symptoms. These therapies include conservative measures such as patient education (to recognize the early symptoms of a syncopal episode and to avoid precipitating factors), increased dietary salt intake and pharmacological interventions with {-blockers, disopyramide or fludrocortisone. On the basis of these study results, it would be reasonable to offer a pacemaker to those patients with frequent symptoms, relative bradycardia on a tilt-table test and who have failed conservative therapy.
Martin J. Gardner, MD Dalhousie University, Halifax, Nova Scotia, Canada
Evidence-based Cardiovascular Medicine (1999) 3, 19
19
Dual-chamber, rate-drop responsive cardiac pacing reduced the risk of syncope among patients with severe recurrent vasovagal syncope Connolly SJ, Sheldon R, Roberts RS, Gent M, on behalf of the Vasovagal Pacemaker Study Investigators. The North American Vasovagal Pacemaker Study (VPS). A randomized trial of permanent cardiac pacing for the prevention of vasovagal syncope. J Am Coll Cardiol 1999;33:16d20
OBJECTIVE To evaluate the effect of permanent dual-chamber cardiac pacing on the risk of syncope among patients with severe recurrent vasovagal syncope.
MAIN OUTCOME MEASURES The primary end-point was the first recurrence of syncope beyond 7 days post-randomization to allow time for the pacemaker group to receive their pacemakers.
DESIGN Multicenter, randomized, controlled clinical trial.
MAIN RESULTS The study was terminated at the first planned interim analysis when a large treatment effect was found which satisfied the pre-specified stopping criteria. The mean time to receiving a pacemaker was 6.7 days (range 1–22 days). There was a significantly lower rate of recurrent syncope in the pacemaker group compared with the control group (22 vs 70%; RRR 85.4%; 95% CI 59.7–94.7%; P"0.000022). The mean times to syncope were 112 and 54 days in the pacemaker and control groups, respectively. During the initial 7 days post-randomization, no patients in the pacemaker group and 6 of 27 patients in the control group experienced syncope. At least one pre-syncopal spell was reported by 63 and 74% of patients in the pacemaker and control groups, respectively. The mean rates of pre-syncopal spells were 4.5 and 10.0 per 100 days in the pacemaker and control groups, respectively.
SETTING Clinical centers in Canada and the USA. PATIENTS 54 of the planned 284 patients with at least six lifetime syncopal spells, and a positive tilt-table test with syncope or presyncope and with relative bradycardia. The mean age was 43 years (46 years in the pacemaker group and 40 years in the control group). Nearly three-quarters were females (70% in pacemaker group and 74% in control group). Patients were excluded if other causes were responsible for loss of consciousness (e.g. ventricular tachycardia, complete heart block, postural hypotension, hypersensitive carotid sinus syndrome or seizures). The median (interquartile range) number of lifetime syncopal spells was 14 (8–35) in the pacemaker group vs 35 (20–100) in the control group. INTERVENTION Patients were randomly allocated to receive either a dual-chamber pacemaker with rate-drop response (minimum rate of 60 beats/minute), or no pacemaker.
Commentary This well-designed study presents the first evidence from a randomized trial that dual-chamber pacing may benefit patients with neurocardiogenic syncope. Neurocardiogenic or vasovagal syncope is common, usually self-limiting and often responds to conservative measures. Occasionally, however, disabling symptoms persist despite conservative and medical therapies. Previous experience with single-chamber VVI pacing has been uniformly disappointing. Non-randomized studies had suggested a benefit of dual-chamber pacing, but this is the first study to use a randomized design. This study was terminated early due to a large treatment effect. As such, the study group is small and there are important differences between the study groups that could have influenced the results. Also, the study was not blinded, with the control group not receiving a pacemaker. With the natural history of neurocardiogenic syncope being so variable, a placebo effect could not be entirely excluded. The pacing group had no decrease in ‘presyncope’, however, strongly supporting the conclusion that pacing was the factor that resulted in the reduction in syncope recurrences. What cannot be determined from this study is whether it was dual chamber pacing itself or the ‘rate-drop’ feature used in this study which provided the treatment effect. These limitations will be addressed in a subsequent study. The patients included were highly selected, with very frequent episodes of syncope and with relative bradycardia on tilt-table testing.
^ 1999 Harcourt Brace & Co. Ltd
CONCLUSION Permanent, dual-chamber, rate-drop responsive cardiac pacing reduced the risk of syncope among patients with severe recurrent vasovagal syncope and a relative bradycardia on tilt-table testing.
Furthermore, it is not clear if patients considered for the study had failed all medical therapy prior to study entry. The results, thus, may not be applicable to the majority of patients with neurocardiogenic syncope. The study results do provide new and exciting evidence that dual-chamber pacing with a rate-drop response may substantially benefit some patients with highly symptomatic neurocardiogenic syncope. The results will be verified in a further study. Until then, it would seem prudent to consider such pacing therapy in selected patients when other therapies have failed to relieve frequent or disabling symptoms. These therapies include conservative measures such as patient education (to recognize the early symptoms of a syncopal episode and to avoid precipitating factors), increased dietary salt intake and pharmacological interventions with {-blockers, disopyramide or fludrocortisone. On the basis of these study results, it would be reasonable to offer a pacemaker to those patients with frequent symptoms, relative bradycardia on a tilt-table test and who have failed conservative therapy.
Martin J. Gardner, MD Dalhousie University, Halifax, Nova Scotia, Canada
Evidence-based Cardiovascular Medicine (1999) 3, 19
19