A Case of Catecholaminergic Polymorphic Ventricular Tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a familial cardiac arrhythmia that is related to RYR2 or CASQ2 gene mutation. It occurs in patients with structurally normal heart and causes exercise-emotion-triggered syncope and sudden cardiac death. We experienced a case of CPVT in an 11 year-old female patient who was admitted for sudden cardiovascular collapse. The initial electrocardiogram (ECG) on emergency department revealed ventricular fibrillation. After multiple defibrillations, sinus rhythm was restored. However, recurrent ventricular fibrillation occurred during insertion of nasogastric tube without sedation in coronary care unit. On ECG monitoring, bidirectional ventricular tachycardia occurred with sinus tachycardia and then degenerated into ventricular fibrillation. To our knowledge, there has been no previous case report of CPVT triggered by sinus tachycardia in Korea. Therefore, we report the case as well as a review of the literature.     

Provocation of bradycardia and hypotension by isoproterenol and upright posture in patients with unexplained syncope

Neurally mediated hypotension and bradycardia are believed to be common causes of syncope. We used the "upright-tilt test" (duration, less than or equal to 10 minutes) with or without an infusion of exogenous catecholamine (isoproterenol [1 to 5 micrograms per minute], given intravenously) to elicit bradycardia, hypotension, or both in 24 patients with recurrent syncope and in 18 control subjects. A conventional electrophysiologic test performed before the tilt test was positive in 9 of the 24 patients, revealing arrhythmias that may have caused recurrent syncope, but was negative and thus nondiagnostic in 15 patients. The tilt test alone (i.e., without isoproterenol) induced symptomatic bradycardia or hypotension in 1 of the 9 patients with positive electrophysiologic tests (11 percent), 4 of the 15 patients with negative electrophysiologic tests (27 percent), and none of the controls. When the isoproterenol infusion was administered during the tilt test, 9 of the 11 patients with negative electrophysiologic and tilt tests had syncope, marked slowing of the heart rate, and hypotension. In contrast, isoproterenol was associated with tachycardia and only a slight decline in arterial pressure in the 8 remaining patients with positive electrophysiologic tests and the 18 control subjects, and syncope developed in only 1 of the 8 patients with positive electrophysiologic tests and negative tilt tests (13 percent) and 2 of the 18 control subjects (11 percent). We conclude that an isoproterenol infusion administered in conjunction with the upright-tilt test may be useful for identifying susceptibility to neurally mediated recurrent syncope.     

The effect of beta adrenergic stimulation on QT and QTc interval in syncope children with or without coexisting ventricular arrhythmias

We investigated the effect of beta-adrenergic stimulation on the heart rate and QT interval in syncope children with or without coexisting ventricular arrhythmias (VA). Of the 24 children who presented with syncope or presyncope and showed negative tilt test, 13 were classified into a group with VA and the remaining 11 without VA. The provocative test was performed in bolus infusion and continuous infusion. RR, QT, and QTc intervals on routine 12-lead surface electrocardiogram were obtained during each stage of isoproterenol infusion. In all cases, malignant ventricular arrhythmia and syncope were not induced by isoproterenol provocative test. RR and QT intervals were shortened and QTc intervals were prolonged as the isoproterenol dose was increased in both groups and methods. The QTc interval reached its peak level after the bolus injection of 1.0 microgram and during the continuous infusion of 0.03 microgram/kg/min. The two groups showed no significant difference in the QTc interval change according to the infusion methods. This study indicates that changes in the heart rate and QT interval by beta-adrenergic stimulation were not different according to the coexisting ventricular arrhythmias in syncope children with negative head-up tilt test.     

Delaying orthostatic syncope with mental challenge: a pilot study

At orthostatic vasovagal syncope there appears to be a sudden decline of sympathetic activity. As mental challenge activates the sympathetic system, we hypothesized that doing mental arithmetic in volunteers driven to the end point of their cardiovascular stability may delay the onset of orthostatic syncope. We investigated this in healthy male subjects. Each subject underwent a head up tilt (HUT)+ graded lower body negative pressure (LBNP) up to presyncope session (control) to determine the orthostatic tolerance time, OTT (Time from HUT commencement to development of presyncopal symptoms/signs). Once the tolerance time was known, a randomized crossover protocol was used: either 1) Repeat HUT+LBNP to ensure reproducibility of repeated run or 2) HUT+LBNP run but with added mental challenge (2 min before the expected presyncope time). Test protocols were separated by 2 weeks. Our studies on five male test subjects indicate that mental challenge improves orthostatic tolerance significantly. Additional mental loading could be a useful countermeasure to alleviate the orthostatic responses of persons, particularly in those with histories of dizziness on standing up, or to alleviate hypotension that frequently occurs during hemodialysis or on return to earth from the spaceflight environment of microgravity.     

Seizure-Like Activities during Head-Up Tilt Test-Induced Syncope

Purpose

Some patients with neurally mediated reflex syncope may be misdiagnosed as epilepsy because myoclonic jerky movements are observed during syncope. The seizure-like activities during the head-up tilt test (HUT) have been rarely reported. The purpose of this study was to assess the characteristics of these seizure-like activities and evaluate whether there are differences in the clinical characteristics and hemodynamic parameters of patients with neurally mediated reflex syncope with and without seizure-like activities during HUT-induced syncope.

Materials and Methods

The medical records of 1,383 consecutive patients with a positive HUT were retrospectively reviewed, and 226 patients were included in this study.

Results

Of 226 patients, 13 (5.75%) showed seizure-like activities, with 5 of these (2.21%) having multifocal myoclonic jerky movements, 5 (2.21%) having focal seizure-like activity involving one extremity, and 3 (1.33%) having upward deviation of eye ball. Comparison of patients with and without seizure-like activities revealed no significant differences in terms of clinical variables and hemodynamic parameters during HUT.

Conclusion

Seizure-like activities occurred occasionally during HUT-induced syncope in patients with neurally mediated reflex syncope. The seizure-like activities during HUT might not be related to the severity of the syncopal episodes or hemodynamic changes during HUT.     

Decreased entropy of symbolic heart rate dynamics during daily activity as a predictor of positive head-up tilt test in patients with alleged neurocardiogenic syncope

Entropy measures of RR interval variability during daily activity over a 24h period were compared in 30 patients with a positive head-up tilt (HUT) test and 30 patients with a negative HUT test who had a history of alleged neurocardiogenic syncope. Two different entropies, approximate entropy (ApEn) and entropy of symbolic dynamics (SymEn), were employed. In patients showing a positive HUT test, the entropies were significantly decreased when compared with the patients with a negative HUT test. In addition, SymEn in the patients with a negative HUT test was significantly lower than in the normal controls. Discriminant analysis using SymEn could correctly identify 89.3% (520/582) of the 1 h RR interval data of the patients with a positive HUT test regardless of the time of day. Baseline entropies of heart rate dynamics during daily activity were found to be significantly lower in patients with alleged neurocardiogenic syncope and a positive HUT test than in those with the same history but with a negative HUT test. The decreased entropy of symbolic heart rate dynamics may be of predictive value of a positive HUT test in patients with alleged neurocardiogenic syncope.     

Sympathetic nerve activity in hypotension and orthostatic intolerance

AIM: The present paper reviews how changes in sympathetic nerve activity are related to hypotensive episodes and orthostatic intolerance in humans. RESULTS: It has been well documented that sympathetic neural traffic to skeletal muscles (muscle sympathetic nerve activity; MSNA) plays an essential role in maintaining blood pressure homeostasis mainly through baroreflex. The MSNA responded to gravitational loading from the head to the leg (+Gz) during passive head-up tilt (HUT). Patients who suffered from orthostatic hypotension with or without syncope were classified into at least two groups; low and high responders of MSNA to orthostatic loading. The typical examples belonging to the former group were patients of multiple system atrophy who had very low basal sympathetic outflow to muscle which responded extremely poorly to HUT. Patients of multiple system atrophy presented also postprandial hypotension in which muscle sympathetic response to oral glucose administration was absent. The latter group was represented by subjects who manifested vasovagal syncope with normal or even higher muscle sympathetic response to HUT, which was suddenly withdrawn concomitantly with bradycardia and hypotension. Similar withdrawal of sympathetic nerve traffic to muscle was encountered in a rare case of idiopathic non-orthostatic episodic hypotension which accompanied bradycardia. The MSNA was suppressed by short-term exposure to microgravity but was enhanced after long-term exposure to microgravity. Orthostatic intolerance after long-term exposure to microgravity was related to progressive reduction of muscle sympathetic response to orthostatic loading with impaired arterial baroreflex. CONCLUSION: It is concluded that hypotensive episodes are closely related to poor or lack of muscle sympathetic outflow, but may depend on various neural mechanisms to induce it.     

Diagnostic value of longterm ambulatory ECG in patients with syncope, dizziness or palpitations

The diagnostic value of longterm ambulatory ECG recording (LTER) was determined in 63 patients referred for investigation of syncope, in 32 with dizziness and in 89 with palpitations. Among patients referred for syncope, dizziness or palpitations 8, 13 and 54%, respectively, had typical symptoms during the recording with concomitant arrhythmia explaining the symptom, and 6, 50 and 11% had a typical symptom without concomitant arrhythmia. In 12 and 3% of the patients referred for syncope or dizziness, respectively, arrhythmia was observed and probably explained their previous complaint, but no symptoms occurred during LTER. LTER was found to be of diagnostic value in 24% of the patients with syncope, in 66% of those with dizziness and in 65% of those with palpitations. In the latter two groups the presence of symptoms the week before the start of these recordings predicted the occurrence of symptoms during LTER. Only occasionally was there a higher yield of typical symptoms beyond 48 h of recording.     

Changes in cardiac rhythm in man during underwater submersion and swimming studied by ECG telemetry

Summary A previously reported method for electrocardiographic (ECG) telemetry in water using frequency-modulated current was improved to obtain more stable ECGs. The ECGs of seven healthy men were monitored using the improved method during and after whole-body submersion or underwater swimming. Bradycardia and arrhythmias were observed during the submersion, and transient tachycardia was detected after the start of underwater swimming, followed by bradycardia with arrhythmias. Three different types of arrhythmias were observed: sinus arrhythmia (SA), supraventricular extra-systole (SE) and ventricular extrasystole (VE). SA and SE tended to develop during the latter half of the period of submersion or underwater swimming, and especially after the restart of breathing. VEs were detected in only one subject during submersion, whereas they occurred in most subjects during and after underwater swimming. Individual variations were found in development of arrhythmias, one subject showing no arrhythmia. Bradycardia, SA and SE could depend on vagal suppression in underwater conditions, and VE may be related to the effect of muscular movement on cardiac function in addition to vagal inhibiton.     

Reducing false alarm rates for critical arrhythmias using the arterial blood pressure waveform

BackgroundOver the past two decades, high false alarm (FA) rates have remained an important yet unresolved concern in the Intensive Care Unit (ICU). High FA rates lead to desensitization of the attending staff to such warnings, with associated slowing in response times and detrimental decreases in the quality of care for the patient. False arrhythmia alarms are commonly due to single channel ECG artifacts and low voltage signals, and therefore it is likely that the FA rates may be reduced if information from other independent signals is used to form a more robust hypothesis of the alarm’s etiology.MethodsA large multi-parameter ICU database (PhysioNet’s MIMIC II database) was used to investigate the frequency of five categories of false critical (“red” or “life-threatening”) ECG arrhythmia alarms produced by a commercial ICU monitoring system, namely: asystole, extreme bradycardia, extreme tachycardia, ventricular tachycardia and ventricular fibrillation/tachycardia. Non-critical (“yellow”) arrhythmia alarms were not considered in this study. Multiple expert reviews of 5386 critical ECG arrhythmia alarms from a total of 447 adult patient records in the MIMIC II database were made using the associated 41,301 h of simultaneous ECG and arterial blood pressure (ABP) waveforms. An algorithm to suppress false critical ECG arrhythmia alarms using morphological and timing information derived from the ABP signal was then tested.ResultsAn average of 42.7% of the critical ECG arrhythmia alarms were found to be false, with each of the five alarm categories having FA rates between 23.1% and 90.7%. The FA suppression algorithm was able to suppress 59.7% of the false alarms, with FA reduction rates as high as 93.5% for asystole and 81.0% for extreme bradycardia. FA reduction rates were lowest for extreme tachycardia (63.7%) and ventricular-related alarms (58.2% for ventricular fibrillation/tachycardia and 33.0% for ventricular tachycardia). True alarm (TA) reduction rates were all 0%, except for ventricular tachycardia alarms (9.4%).ConclusionsThe FA suppression algorithm reduced the incidence of false critical ECG arrhythmia alarms from 42.7% to 17.2%, where simultaneous ECG and ABP data were available. The present algorithm demonstrated the potential of data fusion to reduce false ECG arrhythmia alarms in a clinical setting, but the non-zero TA reduction rate for ventricular tachycardia indicates the need for further refinement of the suppression strategy. To avoid suppressing any true alarms, the algorithm could be implemented for all alarms except ventricular tachycardia. Under these conditions the FA rate would be reduced from 42.7% to 22.7%. This implementation of the algorithm should be considered for prospective clinical evaluation. The public availability of a real-world ICU database of multi-parameter physiologic waveforms, together with their associated annotated alarms is a new and valuable research resource for algorithm developers.     

152例青年学生晕厥患者动态心电图分析

目的:评价动态心电图在青年晕厥患者中的诊断价值。方法:在152例青年晕厥患者中,进行了动态心电图和心电图检查。结果:对窦性心动过速,各种传导阻滞,Q-T间期延长的检出率与普通心电图差异不大,而对窦性静止,快-慢综合征,阵发性室上性心动过速,阵发性室性心动过速动态心电图明显优于普通心电图(P<0.01)。结论:动态心电图为诊断心源性晕厥可提供依据。     

Role of Baroreflex Sensitivity in Predicting Tilt Training Response in Patients with Neurally Mediated Syncope

PurposeAn association between baroreflex sensitivity (BRS) and the response to tilt training has not been reported in patients with neurally mediated syncope (NMS). This study sought to investigate the role of BRS in predicting the response to tilt training in patients with NMS.ResultsAfter tilt training, 52 patients (91.2%) achieved three consecutive negative responses to the HUT. In the supine position before upright posture during the first session of tilt training for responders and non-responders, the mean BRS was 18.17±10.09 ms/mm Hg and 7.99±5.84 ms/mm Hg (p=0.008), respectively, and the frequency of BRS ≥8.945 ms/mm Hg was 45 (86.5%) and 1 (20.0%; p=0.004), respectively. Age, male gender, frequency of syncopal events before HUT, type of NMS, phase of positive HUT, total number of tilt training sessions, and mean time of tilt training did not differ between the study groups. In the multivariate analysis, BRS <8.945 ms/mm Hg in the supine position (odds ratio 23.10; 95% CI 1.20-443.59; p=0.037) was significantly and independently associated with non-response to tilt training.ConclusionThe BRS value in the supine position could be a predictor for determining the response to tilt training in patients with NMS who are being considered for inpatient tilt training.     

Sustained arrhythmias in hypertrophic obstructive cardiomyopathy

Patients with hypertrophic obstructive cardiomyopathy are subject to syncope and sudden death. Ambulatory monitoring discloses frequent and complex ventricular ectopy in many of these patients, and the occurrence of ventricular tachycardia suggests an increased risk of sudden death. We prospectively evaluated whether induced sustained arrhythmia could explain episodes of cerebral dysfunction in hypertrophic cardiomyopathy. Seven consecutive symptomatic patients (six of whom had an intraventricular gradient of 40 to 130 mm Hg) were subjected to atrial and ventricular stimulation. An electrophysiologic abnormality that would explain the symptoms was identified in every patient: supraventricular tachycardia was present in two, sustained ventricular tachycardia in three, ventricular fibrillation in one, and a prolonged QT interval and dispersion of ventricular refractoriness in one. Antiarrhythmic drugs were selected on the basis of the response to electrophysiologic testing. There has been no recurrence of symptoms in 120 patient-months of follow-up. This experience suggests that arrhythmias are the principal cause of syncope or sudden death in obstructive cardiomyopathy and that electrophysiologic study may be useful in selecting prophylactic therapy.     

新生儿心律失常56例临床分析

本文报道经临床表现和心电图确诊新生儿心律失常56例,其中房性早搏15例(26.7%),室性早搏12例(21.4%),室上性阵发性心动过速10例(17.8%),先天性房室传导阻滞6例(10.6%),窦性心动过缓6例(10. 6%),右束支阻滞6例(10.6%),新生儿心律失常类型以房性早搏最多:其次是室性早搏、室上性阵发性心动过速、房室传导阻滞.新生儿心律失常的病因以感染为主,本文感染29例(51.7%),其次心脏结构异常,先天性房室传导阻滞6例(10.6%),文中讨论了新生儿心律失常的治疗及其结果.     

Beat-to-beat noninvasive stroke volume from arterial pressure and Doppler ultrasound

The proper understanding of the cardiovascular mechanisms involved in complaints of short-lasting dizziness and the evaluation of unexplained recurrent syncope requires continuous monitoring of cardiac stroke volume (SV) in addition to blood pressure and heart rate. The primary aim of the present study was to evaluate a pulse wave analysis method that calculates beat-to-beat flow from non-invasive arterial pressure by simulating a non-linear, time-varying model of human aortic input impedance (Modelflow; MF), by comparing MF stroke volume (SV_MF) to Doppler ultrasound (US) flow velocity SV (SV_US). A second purpose was to compare the two methods under two different conditions: the supine and head-up tilt (30°) position. SV_US and SV_MF with non-invasive arterial pressure (Finapres) as input to the aortic model were measured beat-to-beat during spontaneous supine breathing and in the passive 30° head-up tilt (HUT30) position in six normotensive healthy humans [three females, mean age 24 (21–26) years]. There were variations in supine SV track between the two methods with zero difference and a SD of the beat-to-beat difference (MF–US) of 4.2%. HUT30 induced a systematic difference of 10.5% and an increase in SD to 6.9%, which was reproducible. Beat-to-beat changes in SV in the supine resting condition were equally well assessed by both methods. Systematic differences appear during HUT30 and show opposite signs. The difference between the two methods upon a change in body position may be attributed to limitations in each method.     

Heart rate and sustained attention during childhood: Age changes in anticipatory heart rate, primary bradycardia, and respiratory sinus arrhythmia

This study examined age changes in three aspects of heart rate responsivity elicited in an auditory oddball task; anticipatory heart rate change, primary bradycardia, and respiratory sinus arrhythmia. Three age groups (5-, 7-, and 9-year-old boys) were presented with series of target (15%) and standard (85%) tones. The results were consistent with the findings reported previously in the adult literature. Heart rate decreased in anticipation of the target tone. The morphology of anticipatory deceleration was somewhat different for the 5-year-olds compared to the older children. Stimuli presented during the early part of the cardiac cycle induced added deceleration, but this primary bradycardia did not differ between age groups. Respiratory sinus arrhythmia did not discriminate between age groups but was suppressed during the performance of the oddball task relative to base level. It was concluded that these three aspects of heart rate responsivity show developmental constancy rather than change.     

Gender Difference in Patients with Recurrent Neurally Mediated Syncope

Purpose

The gender difference of neurally mediated syncope is not well defined in a large patient population. The aim of this study was to evaluate the gender difference of clinical manifestations in patients with neurally mediated syncope who underwent head-up tilt test.

Materials and Methods

The medical records of 1,051 consecutive patients with two or more episodes of syncope, who were diagnosed as having neurally mediated syncope by head-up tilt test, were retrospectively reviewed.

Results

Of 1,051 patients, 497 (47.3%) patients were male and 554 (52.7%) patients were female. Female patients were experiencing syncopal episodes for longer periods of their lives (8.2 ± 9.5 years vs. 6.8 ± 9.2 years, p = 0.002) and more episodes of syncope prior to head-up tilt test (HUT) (7.2 ± 9.4 vs. 5.0 ± 6.4, p = 0.001) than male patients. Micturition syncope (20.0% vs. 5.2%, p < 0.001) was observed more frequently in male patients than in female patients. To the contrary, however, defecation syncope (16.3% vs. 9.3%, p < 0.001) was observed more frequently in female patients than in male patients.

Conclusion

Female patients were experiencing syncopal episodes for longer periods of their lives and more episodes of syncope than male patients. Gender difference was also noted with regard to frequency of situational syncope.     

Autonomic cardiovascular response to acute hypoxia and passive head-up tilting in humans

Acute hypoxia may alter autonomic cardiovascular reflexes during orthostasis. Heart rate variability (HRV), arterial blood pressure (MAP), and respiratory sinus arrhythmia (RSA) were recorded during supine (SUP) and passive head up tilt (HUT) in eight healthy humans, spontaneously breathing either room air or 10 % O₂ in N₂. In the time domain, heart rate increased and variability decreased with HUT in both trials, with no difference between trials. In the frequency domain, normalized low frequency HRV increased, and normalized high frequency HRV decreased with HUT in both trials, with no difference between trials. MAP was 74.9 (8.6) and 77.5 (11.7) mmHg when SUP in the room air and hypoxia trials, respectively. A significant increase in MAP occurred with HUT in the room air trial but not in the hypoxia trial. In both trials, end tidal CO₂ decreased with HUT, with no difference between trials. In the room air trial, end tidal O₂ increased with HUT, whereas during the hypoxia trial, end tidal O₂ decreased with HUT. The distribution of heart beats relative to the phase of ventilation (%HB_IN and %HB_OUT) was similar in both trials: the %HB_IN was 43.5 (3.3) % and %HB_OUT was 56.5 (4.2) % breathing room air when SUP, and 45.5 (3.0) and 54.5 (3.2) when hypoxic and SUP. For both trials, this distribution did not change with HUT. As both HRV and RSA showed similar responses to HUT when spontaneously breathing either room air or 10 % O₂ in N₂, we suggest that autonomic cardiovascular reflexes are preserved during acute hypoxia.     

Anaphylaxis associated with relative bradycardia

A 31-year-old man with allergic rhinoconjunctivitis and asthma experienced an episode of anaphylaxis following an injection of allergens during hyposensitization. His anaphylactic episode was remarkable because of a relative sinus bradycardia at the beginning of his reaction. This case is reported to highlight the importance of not confusing the anaphylactic syndrome with vasovagal syncope even when a tachycardia is initially absent. The possible pathophysiologic role of right coronary vasospasm resulting in the Bezold-Jarish reflex or sinoatrial node ischemia is discussed.     

Efficacy of flecainide in bidirectional ventricular tachycardia and tachycardia-induced cardiomyopathy with Andersen-Tawil syndrome

Andersen-Tawil syndrome is a rare autosomal dominant genetic or sporadic disorder characterized by periodic paralysis, ventricular arrhythmias and dysmorphic features. Ventricular arrhythmias can include frequent premature ventricular complex, polymorphic ventricular tachycardia, and less frequently bidirectional ventricular tachycardia. Left ventricle function has been reported in only a few individual cases of Andersen-Tawil syndrome. A 14-year-old female patient was referred to our clinic from another center with documented arrhythmia and left ventricular systolic dysfunction. Andersen-Tawil syndrome was suspected and the diagnosis was confirmed after detection of a previously unreported mutation in children. We report the successful use of flecainide in bidirectional ventricular tachycardia and tachycardia-induced cardiomyopathy in a case of Andersen-Tawil syndrome associated with a novel mutation.