In programming the implantable cardioverter defibrillator (ICD), the ventricular tachycardia (VT)... more In programming the implantable cardioverter defibrillator (ICD), the ventricular tachycardia (VT) detection cycle length (CL) is based on the CL of the documented tachycardia but the ventricular fibrillation (VF) detection CL is set arbitrarily. Appropriate programming of VF detection may not only reduce the incidence of inappropriate ICD shocks for non-VF rhythms but can also avoid the fatal underdetection of VF. The mean VFCL may provide a useful parameter for optimal ICD programming for VF detection if it is reproducible. This study examined the intrapatient reproducibility and interpatient variation of the mean VFCL in 30 ICD patients (25 men and 5 women, mean age 63 ± 13 years). A total of 210 VF episodes (7 ± 4 per patient, range 3–17) induced by T-wave shocks (166) or AC (44) at the ICD implant (30 patients) and the predischarge test (12 of 30 patients) were analyzed. The mean VFCL was calculated from the stored V-V intervals in the ICDs. Although the mean VFCL varied significantly from 171 ± 6 to 263 ± 11 ms (P < 0.01) among different patients, it was reproducible among different VF episodes in an individual patient (maximal variation 4–50 ms, P > 0.05). The mean VFCL was not significantly different between patients with and without antiarrhythmic drugs (210 ± 32 vs 210 ± 23 ms, P > 0.05) and was correlated with the ventricular effective refractory period (r = 0.5, P < 0.05). The mean VFCL varies greatly among different patients but remains reproducible in an individual patient, suggesting that the mean VFCL may serve as a reference for ICD programming of VF detection.
Serotonin (5-hydroxytryptamine or 5HT) is a neurotransmitter which appears to play a prominent ro... more Serotonin (5-hydroxytryptamine or 5HT) is a neurotransmitter which appears to play a prominent role in central regulation of heart rate and blood pressure. Recent evidence suggests that the activation of cerebral serotonin receptors results in a depressor effect principally through sympatho-inhibition. Several common clinical disorders resulting in hypotension leading to syncope are neurally mediated syncope, carotid sinus hypersensitivity and orthostatic hypotension, each of which may involve a serotonergic component. This brief review provides a summary of serotonergic blood pressure regulation, as well as the initial experience with the clinical effects of the serotonin reuptake inhibitors in the therapy of the aforementioned disorders.
Recurrent vasovagally mediated episodes of hypotension and bradycardia are a common cause of recu... more Recurrent vasovagally mediated episodes of hypotension and bradycardia are a common cause of recurrent syncope that can be identified by head-upright tilt table testing. Although the use of beta blockers, transdermal scopolamine, disopyramide, and fludrocortisone may be helpful in preventing further episodes, some patients are intolerant of or respond poorly to each of these agents. Following anecdotal observations, we investigated the utility of fluoxetine (a serotonin re-uptake antagonist) in preventing head-upright tilt induced hypotension/bradycardia in patients unresponsive to or intolerant of standard therapy. Sixteen patients (7 men and 9 women, mean age 42 ± 21 years) with recurrent syncope and positive head-upright tilt studies (refractory to normal therapy) were placed on fluoxetine and restudied 5–6 weeks afterward. Three patients were intolerant of the medication. Of the 13 patients who underwent repeat tilt studies, seven patients (53% of the patients retested or 44% of the total group) were rendered tilt table negative, and, over a mean follow-up period of 19 ± 9 months, have remained asymptomatic. We conclude that fluoxetine may be an effective therapy in patients with recurrent vasovagally mediated syncope refractory to other forms of therapy.
Psychogenic seizures and psychogenic syncope are common disorders but are difficult to identify. ... more Psychogenic seizures and psychogenic syncope are common disorders but are difficult to identify. Head-upright tilt table testing has emerged as a promising means of evaluating vasovagally mediated syncope and convulsive syncope. Of a total of 42 patients evaluated by head-up tilt for recurrent syncope and 10 evaluated for recurrent idiopathic seizures, a total of 5 patients experienced syncope and 3 had tonic-clonic seizure activity unaccompanied by any significant changes in blood pressure, heart rate, transcranial Doppler cerebral blood flow velocity, and electroencephalographic monitoring. Psychiatric evaluation revealed that seven patients suffered from conversion reactions and one from probable malingering. We conclude that patients who pass out or convulse during head-upright tilt without any change in physiologic parameters can be presumed psychogenic in origin and may be referred for psychiatric evaluation without further expensive diagnostic studies.
Recurrent idiopathic exercise-related syncope in the young athlete is often a challenging and fru... more Recurrent idiopathic exercise-related syncope in the young athlete is often a challenging and frustrating condition. Vasovagally mediated hypotension and bradycardia is believed to be a common, but difficult to prove, cause of this form of syncope. This study evaluated the usefulness of head-upright tilt table testing in the evaluation and management of young athletes with recurrent idiopathic exercise-related syncope. Twenty-four trained young athletes (12 male, 12 female mean age 18 +/- 3.4 yr) with recurrent unexplained exercise-related syncope were evaluated by use of an upright tilt table test for 30 min, with or without an infusion of isoproterenol (1-3 micrograms.min-1 given intravenously) in an effort to provoke bradycardia, hypotension, or both. Ten control patients with no history of syncope were also studied. Syncope occurred in 10 patients (41%) during the baseline tilt and in nine patients (37%) during the isoproterenol infusion (total positives 79%). Seventeen patients who had positive test results eventually became tilt table negative with pharmacotherapy, and over a mean follow-up period of 23 +/- 7 months, no further syncopal episodes have occurred. Two patients refused pharmacotherapy and have continued to experience syncope. We conclude that head-upright tilt table testing combined with isoproterenol infusion is useful in the diagnosis of vasovagal syncope in young athletes with recurrent exercise related syncope, and in the evaluation of prophylactic pharmacotherapy.
Transcranial Doppler (TCD) ultrasonography done during headupright tilt induced neurocardiogenic ... more Transcranial Doppler (TCD) ultrasonography done during headupright tilt induced neurocardiogenic syncope has demonstrated that cerebral Vasoconstriction occurs concomitant with (or precedes) loss of consciousness. This article demonstrates evidence that cerebral blood flow changes alone (vasoconstriction), in the absence of systemic hypotension, may result in syncope. Five patients (4 men, 1 woman; mean age 41 ± 17 years) with recurrent unexplained syncope were evaluated by use of an upright tilt table test for 45 minutes with or without an infusion of low dose isoproterenol. TCDoppler ultrasonography was used to assess middle cerebral artery systolic velocity (Vs); diastolic velocity (Vd); mean velocity (Vm); and pulsatility index (PI = Vs = Vd/Vmean). Syncope occurred in five patients during the baseline tilt and in one patient during isoproterenol infusion. During tilt induced syncope, at an average mean arterial pressure of 89 ± 16 mmHg, TCD sonography showed a 2%± 10% increase in systolic velocity; a 51%± 27% decrease in diastolic velocity; and a 131 %± 87% increase in pulsatility index. One patient underwent continuous electroencephalographic recording during tilt, which demonstrated diffuse slow wave activity (indicating cerebral hypoxia) at the time of syncope concomitant with the aforementioned TCD changes in the absence of systemic hypotension. These fndings reflect an increase in cerebrovascular resistance secondary to arteriolar vasoconstriction distal to the insonation point of the middle cerebral artery, that occurred concomitant with loss of consciousness and in the absence of systemic hypotension. We conclude that in some individuals abnormal baroreceptor responses triggered during orthostatic stress may result in a derangement of cerebral autoregulation leading to cerebral vasoconstriction with resultant cerebral hypoxia in the absence of systemic hypotension.
Recurrent episodes of unexplained syncope are a common and often frustrating problem for the prac... more Recurrent episodes of unexplained syncope are a common and often frustrating problem for the practicing physician. Although vasovagally mediated episodes of hypotension and bradycardia have been felt to be a common cause of these idiopathic events, traditionally this was a diagnosis of exclusion. Recently, head-upright tilt table testing has emerged as a method both for confirming the diagnosis of vasovagal syncope and for better understanding the mechanisms by which these events occur. This paper reviews current understanding of the pathophysiology of vasovagal syncope, the development and role of head-upright tilt table testing in its evaluation, and potential therapeutic modalities that can be helpful for the prevention of recurrent episodes.
Sotalol was developed as a nonselective beta-blocker in the 1960s for the treatment of hypertensi... more Sotalol was developed as a nonselective beta-blocker in the 1960s for the treatment of hypertension and later for cardiac risk management after myocardial infarction. Extensive research has since well described class III type electrophysiologic effects on the repolarization of myocardial fibers. Sotalol prolongs and homogenizes ventricular refractoriness, resulting in good antifibrillatory/antitachycardia protection. The unique combination of beta-blockade and antiarrhythmic effects probably will promote sotalol&#39;s use in postmyocardial infarction patients with ventricular tachycardia and sudden death. This article summarizes the pharmacologic and cardiovascular effects of this new drug, outlining its clinical use.
Carotid sinus hypersensitivity can be a cause of recurrent unexplained syncope in the older patie... more Carotid sinus hypersensitivity can be a cause of recurrent unexplained syncope in the older patient. Dual chamber cardiac pacing may relieve the bradycardia, but may not affect the vasodilatory component of this disorder. We report on two patients with carotid sinus hypersensitivity with a predominant vasodilatory component who experienced recurrent syncope following permanent pacemaker implantation. Both patients were treated with serotonin reuptake inhibitors and after 4–6 weeks of therapy had complete resolution of symptoms. We conclude that serotonin reuptake inhibitors may be useful in the treatment of recurrent syncope due to carotid sinus hypersensitivity resistant to dual chamber cardiac pacing.
A 72-year-old African-American man with frequent recurrent syncope was found to have severe refra... more A 72-year-old African-American man with frequent recurrent syncope was found to have severe refractory orihostatic hypotension with concomitant supine hypertension. Pharmacotherupy was successful in controlling his supine hypertension but was unable to resolve his severe orihostatic hypotension. Temporary fixed rate tachypacing was only minimally effective in preventing syncope during upright tilt, while variable rate pacing based on degree of blood pressure fall was far superior. Following these observations, an adaptive rate pacing system controlled by right ventricular preejection interval was implanted (Precept DR Model 1200). The system adequately sensed the patient's fall in blood pressure when sitting or standing and augmented its rate accordingly, thus preventing syncope. While supine, the pacing rate fell to 60 ppm, thereby, avoiding an exacerbation of his concomitant supine hypertension. Over a 3-nionth follow-up period, he has had no further orthostatic or syncopal episodes. We conclude that adaptive rate pacing using right ventricular preejection interval may be an effective treatment for severe refractory orthostatic hypotension.
Recurrent unexpected syncope may have severe consequences and result in serious injury. This is e... more Recurrent unexpected syncope may have severe consequences and result in serious injury. This is especially the case in the immediate postpartum period when maternal syncope may have a disastrous effect on the infant as well as the mother. We report on 12 women who developed episodic hypotension resulting in syncope in the immediate postpartum period and describe the distinguishing characteristics of their presentation, tilt table results, and responses to therapy. Postpartum syncope represents a unique subgroup of syncopal patients who need to be recognized and treated in order to prevent potentially serious injury to both mother and infant.
To evaluate the usefulness of fluoxetine hydrochloride in the treatment of patients with severe r... more To evaluate the usefulness of fluoxetine hydrochloride in the treatment of patients with severe refractory orthostatic hypotension. Prospective, nonrandomized study. Five patients (3 men, 2 women with a mean age of 67 +/- 7 years with chronic symptomatic orthostatic hypotension resistant to or intolerant of other therapies. Symptoms and orthostatic responses were recorded in the baseline state. Fluoxetine hydrochloride 20 mg orally once daily was started and patients were reevaluated after 6 to 8 weeks of therapy. All patients demonstrated orthostatic hypotension (20 mm Hg or greater decline in systolic blood pressure) associated with symptoms (eg, dizziness, vertigo, near syncope) in the baseline state. After 6 to 8 weeks of fluoxetine therapy, 2 patients reported resolution of all symptoms, 2 had a marked reduction in symptoms, and 1 patient experienced no effect. Orthostatic responses were attenuated in 4 of the 5 patients (80%). Fluoxetine hydrochloride may be an effective therapy for some patients with recurrent severe orthostatic hypotension refractory to other forms of therapy.
In programming the implantable cardioverter defibrillator (ICD), the ventricular tachycardia (VT)... more In programming the implantable cardioverter defibrillator (ICD), the ventricular tachycardia (VT) detection cycle length (CL) is based on the CL of the documented tachycardia but the ventricular fibrillation (VF) detection CL is set arbitrarily. Appropriate programming of VF detection may not only reduce the incidence of inappropriate ICD shocks for non-VF rhythms but can also avoid the fatal underdetection of VF. The mean VFCL may provide a useful parameter for optimal ICD programming for VF detection if it is reproducible. This study examined the intrapatient reproducibility and interpatient variation of the mean VFCL in 30 ICD patients (25 men and 5 women, mean age 63 ± 13 years). A total of 210 VF episodes (7 ± 4 per patient, range 3–17) induced by T-wave shocks (166) or AC (44) at the ICD implant (30 patients) and the predischarge test (12 of 30 patients) were analyzed. The mean VFCL was calculated from the stored V-V intervals in the ICDs. Although the mean VFCL varied significantly from 171 ± 6 to 263 ± 11 ms (P < 0.01) among different patients, it was reproducible among different VF episodes in an individual patient (maximal variation 4–50 ms, P > 0.05). The mean VFCL was not significantly different between patients with and without antiarrhythmic drugs (210 ± 32 vs 210 ± 23 ms, P > 0.05) and was correlated with the ventricular effective refractory period (r = 0.5, P < 0.05). The mean VFCL varies greatly among different patients but remains reproducible in an individual patient, suggesting that the mean VFCL may serve as a reference for ICD programming of VF detection.
Serotonin (5-hydroxytryptamine or 5HT) is a neurotransmitter which appears to play a prominent ro... more Serotonin (5-hydroxytryptamine or 5HT) is a neurotransmitter which appears to play a prominent role in central regulation of heart rate and blood pressure. Recent evidence suggests that the activation of cerebral serotonin receptors results in a depressor effect principally through sympatho-inhibition. Several common clinical disorders resulting in hypotension leading to syncope are neurally mediated syncope, carotid sinus hypersensitivity and orthostatic hypotension, each of which may involve a serotonergic component. This brief review provides a summary of serotonergic blood pressure regulation, as well as the initial experience with the clinical effects of the serotonin reuptake inhibitors in the therapy of the aforementioned disorders.
Recurrent vasovagally mediated episodes of hypotension and bradycardia are a common cause of recu... more Recurrent vasovagally mediated episodes of hypotension and bradycardia are a common cause of recurrent syncope that can be identified by head-upright tilt table testing. Although the use of beta blockers, transdermal scopolamine, disopyramide, and fludrocortisone may be helpful in preventing further episodes, some patients are intolerant of or respond poorly to each of these agents. Following anecdotal observations, we investigated the utility of fluoxetine (a serotonin re-uptake antagonist) in preventing head-upright tilt induced hypotension/bradycardia in patients unresponsive to or intolerant of standard therapy. Sixteen patients (7 men and 9 women, mean age 42 ± 21 years) with recurrent syncope and positive head-upright tilt studies (refractory to normal therapy) were placed on fluoxetine and restudied 5–6 weeks afterward. Three patients were intolerant of the medication. Of the 13 patients who underwent repeat tilt studies, seven patients (53% of the patients retested or 44% of the total group) were rendered tilt table negative, and, over a mean follow-up period of 19 ± 9 months, have remained asymptomatic. We conclude that fluoxetine may be an effective therapy in patients with recurrent vasovagally mediated syncope refractory to other forms of therapy.
Psychogenic seizures and psychogenic syncope are common disorders but are difficult to identify. ... more Psychogenic seizures and psychogenic syncope are common disorders but are difficult to identify. Head-upright tilt table testing has emerged as a promising means of evaluating vasovagally mediated syncope and convulsive syncope. Of a total of 42 patients evaluated by head-up tilt for recurrent syncope and 10 evaluated for recurrent idiopathic seizures, a total of 5 patients experienced syncope and 3 had tonic-clonic seizure activity unaccompanied by any significant changes in blood pressure, heart rate, transcranial Doppler cerebral blood flow velocity, and electroencephalographic monitoring. Psychiatric evaluation revealed that seven patients suffered from conversion reactions and one from probable malingering. We conclude that patients who pass out or convulse during head-upright tilt without any change in physiologic parameters can be presumed psychogenic in origin and may be referred for psychiatric evaluation without further expensive diagnostic studies.
Recurrent idiopathic exercise-related syncope in the young athlete is often a challenging and fru... more Recurrent idiopathic exercise-related syncope in the young athlete is often a challenging and frustrating condition. Vasovagally mediated hypotension and bradycardia is believed to be a common, but difficult to prove, cause of this form of syncope. This study evaluated the usefulness of head-upright tilt table testing in the evaluation and management of young athletes with recurrent idiopathic exercise-related syncope. Twenty-four trained young athletes (12 male, 12 female mean age 18 +/- 3.4 yr) with recurrent unexplained exercise-related syncope were evaluated by use of an upright tilt table test for 30 min, with or without an infusion of isoproterenol (1-3 micrograms.min-1 given intravenously) in an effort to provoke bradycardia, hypotension, or both. Ten control patients with no history of syncope were also studied. Syncope occurred in 10 patients (41%) during the baseline tilt and in nine patients (37%) during the isoproterenol infusion (total positives 79%). Seventeen patients who had positive test results eventually became tilt table negative with pharmacotherapy, and over a mean follow-up period of 23 +/- 7 months, no further syncopal episodes have occurred. Two patients refused pharmacotherapy and have continued to experience syncope. We conclude that head-upright tilt table testing combined with isoproterenol infusion is useful in the diagnosis of vasovagal syncope in young athletes with recurrent exercise related syncope, and in the evaluation of prophylactic pharmacotherapy.
Transcranial Doppler (TCD) ultrasonography done during headupright tilt induced neurocardiogenic ... more Transcranial Doppler (TCD) ultrasonography done during headupright tilt induced neurocardiogenic syncope has demonstrated that cerebral Vasoconstriction occurs concomitant with (or precedes) loss of consciousness. This article demonstrates evidence that cerebral blood flow changes alone (vasoconstriction), in the absence of systemic hypotension, may result in syncope. Five patients (4 men, 1 woman; mean age 41 ± 17 years) with recurrent unexplained syncope were evaluated by use of an upright tilt table test for 45 minutes with or without an infusion of low dose isoproterenol. TCDoppler ultrasonography was used to assess middle cerebral artery systolic velocity (Vs); diastolic velocity (Vd); mean velocity (Vm); and pulsatility index (PI = Vs = Vd/Vmean). Syncope occurred in five patients during the baseline tilt and in one patient during isoproterenol infusion. During tilt induced syncope, at an average mean arterial pressure of 89 ± 16 mmHg, TCD sonography showed a 2%± 10% increase in systolic velocity; a 51%± 27% decrease in diastolic velocity; and a 131 %± 87% increase in pulsatility index. One patient underwent continuous electroencephalographic recording during tilt, which demonstrated diffuse slow wave activity (indicating cerebral hypoxia) at the time of syncope concomitant with the aforementioned TCD changes in the absence of systemic hypotension. These fndings reflect an increase in cerebrovascular resistance secondary to arteriolar vasoconstriction distal to the insonation point of the middle cerebral artery, that occurred concomitant with loss of consciousness and in the absence of systemic hypotension. We conclude that in some individuals abnormal baroreceptor responses triggered during orthostatic stress may result in a derangement of cerebral autoregulation leading to cerebral vasoconstriction with resultant cerebral hypoxia in the absence of systemic hypotension.
Recurrent episodes of unexplained syncope are a common and often frustrating problem for the prac... more Recurrent episodes of unexplained syncope are a common and often frustrating problem for the practicing physician. Although vasovagally mediated episodes of hypotension and bradycardia have been felt to be a common cause of these idiopathic events, traditionally this was a diagnosis of exclusion. Recently, head-upright tilt table testing has emerged as a method both for confirming the diagnosis of vasovagal syncope and for better understanding the mechanisms by which these events occur. This paper reviews current understanding of the pathophysiology of vasovagal syncope, the development and role of head-upright tilt table testing in its evaluation, and potential therapeutic modalities that can be helpful for the prevention of recurrent episodes.
Sotalol was developed as a nonselective beta-blocker in the 1960s for the treatment of hypertensi... more Sotalol was developed as a nonselective beta-blocker in the 1960s for the treatment of hypertension and later for cardiac risk management after myocardial infarction. Extensive research has since well described class III type electrophysiologic effects on the repolarization of myocardial fibers. Sotalol prolongs and homogenizes ventricular refractoriness, resulting in good antifibrillatory/antitachycardia protection. The unique combination of beta-blockade and antiarrhythmic effects probably will promote sotalol&#39;s use in postmyocardial infarction patients with ventricular tachycardia and sudden death. This article summarizes the pharmacologic and cardiovascular effects of this new drug, outlining its clinical use.
Carotid sinus hypersensitivity can be a cause of recurrent unexplained syncope in the older patie... more Carotid sinus hypersensitivity can be a cause of recurrent unexplained syncope in the older patient. Dual chamber cardiac pacing may relieve the bradycardia, but may not affect the vasodilatory component of this disorder. We report on two patients with carotid sinus hypersensitivity with a predominant vasodilatory component who experienced recurrent syncope following permanent pacemaker implantation. Both patients were treated with serotonin reuptake inhibitors and after 4–6 weeks of therapy had complete resolution of symptoms. We conclude that serotonin reuptake inhibitors may be useful in the treatment of recurrent syncope due to carotid sinus hypersensitivity resistant to dual chamber cardiac pacing.
A 72-year-old African-American man with frequent recurrent syncope was found to have severe refra... more A 72-year-old African-American man with frequent recurrent syncope was found to have severe refractory orihostatic hypotension with concomitant supine hypertension. Pharmacotherupy was successful in controlling his supine hypertension but was unable to resolve his severe orihostatic hypotension. Temporary fixed rate tachypacing was only minimally effective in preventing syncope during upright tilt, while variable rate pacing based on degree of blood pressure fall was far superior. Following these observations, an adaptive rate pacing system controlled by right ventricular preejection interval was implanted (Precept DR Model 1200). The system adequately sensed the patient's fall in blood pressure when sitting or standing and augmented its rate accordingly, thus preventing syncope. While supine, the pacing rate fell to 60 ppm, thereby, avoiding an exacerbation of his concomitant supine hypertension. Over a 3-nionth follow-up period, he has had no further orthostatic or syncopal episodes. We conclude that adaptive rate pacing using right ventricular preejection interval may be an effective treatment for severe refractory orthostatic hypotension.
Recurrent unexpected syncope may have severe consequences and result in serious injury. This is e... more Recurrent unexpected syncope may have severe consequences and result in serious injury. This is especially the case in the immediate postpartum period when maternal syncope may have a disastrous effect on the infant as well as the mother. We report on 12 women who developed episodic hypotension resulting in syncope in the immediate postpartum period and describe the distinguishing characteristics of their presentation, tilt table results, and responses to therapy. Postpartum syncope represents a unique subgroup of syncopal patients who need to be recognized and treated in order to prevent potentially serious injury to both mother and infant.
To evaluate the usefulness of fluoxetine hydrochloride in the treatment of patients with severe r... more To evaluate the usefulness of fluoxetine hydrochloride in the treatment of patients with severe refractory orthostatic hypotension. Prospective, nonrandomized study. Five patients (3 men, 2 women with a mean age of 67 +/- 7 years with chronic symptomatic orthostatic hypotension resistant to or intolerant of other therapies. Symptoms and orthostatic responses were recorded in the baseline state. Fluoxetine hydrochloride 20 mg orally once daily was started and patients were reevaluated after 6 to 8 weeks of therapy. All patients demonstrated orthostatic hypotension (20 mm Hg or greater decline in systolic blood pressure) associated with symptoms (eg, dizziness, vertigo, near syncope) in the baseline state. After 6 to 8 weeks of fluoxetine therapy, 2 patients reported resolution of all symptoms, 2 had a marked reduction in symptoms, and 1 patient experienced no effect. Orthostatic responses were attenuated in 4 of the 5 patients (80%). Fluoxetine hydrochloride may be an effective therapy for some patients with recurrent severe orthostatic hypotension refractory to other forms of therapy.
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Papers by Daniela Samoil