Magnetocardiography in the evaluation of fetuses at risk for sudden cardiac death before birth

Background

We hypothesized that fetuses at risk for sudden death may have abnormal conduction or depolarization, ischemia, or abnormal heart rate variability (HRV) detectable by magnetocardiography.

Methods

Using a 37-channel biomagnetometer, we evaluated 3 groups of fetuses at risk for sudden death: group 1, critical aortic stenosis (AS); group 2, arrhythmias; and group 3, heart failure and in utero demise. Five to 10 recordings of 10-minute duration were recorded, and signal was averaged to determine rhythm, conduction intervals, HRV, and T-wave morphology.

Results

In group 1, 2 of 3 had atrial and ventricular strain patterns. In (n = 53) group 2, 15% had prolonged QTc and 17% had T-wave alternans (TWA). Of 23 group 2 fetuses with atrioventricular block, 74% had ventricular ectopy, 21% had junctional ectopic tachycardia, and 29% had ventricular tachycardia. Group 3 (n = 2) had abnormal HRV and TWA.

Conclusion

Repolarization abnormalities, unexpected arrhythmias, and abnormal HRV suggest an arrhythmogenic mechanism for “sudden cardiac death before birth.”     

Characterization and incidence of inducible monomorphic ventricular tachycardia in a postinfarction rabbit model

Objective

Ventricular tachycardia (VT), occurring late after myocardial infarction, is an important cause of sudden death. Animal models are useful for the investigation of this arrhythmia. The aim of this study is to develop and characterize a model of late postinfarction monomorphic VT in the rabbit.

Methods and Results

Myocardial infarction was created by ligation of the left circumflex artery. Cardiac electrophysiologic studies were performed 10 to 17 days postinfarction in 39 rabbits, in 10 sham-operated rabbits, and 6 control rabbits. Ventricular tachycardia was defined as a broad-complex tachycardia with a cycle length of more than 100 milliseconds, a duration of more than 10 seconds, and monomorphic QRS complexes. Using programmed stimulation, we induced VT in 9 rabbits (23%) in the infarct group but in none of the sham or control animals. The mean infarct size was 23% ± 9% (mean ± SD) of the left ventricle.

Conclusion

Coronary ligation in the rabbit creates a substrate, which allows the induction of sustained monomorphic VT with programmed stimulation. Monomorphic VT is not inducible in rabbits without myocardial infarction. This model might allow the testing of interventions that reduce the incidence of VT late after myocardial infarction.     

Effect of first ventricular tachycardia cycle length on rate of ventricular arrhythmia recurrence in patients with implantable cardioverter-defibrillator

Background

Some controversies exist regarding the proper treatment of hemodynamically tolerated and slow ventricular tachycardia (VT). We intended to assess the effect of cycle length of first VT episode on total ventricular arrhythmia burden in a cohort of patients with implantable cardioverter-defibrillator (ICD).

Method

Between March 2000 and March 2005, 195 patients underwent ICD implantation at our center. We included 158 patients (mean age, 58.3 ± 12.9 years) with follow-up of 3 months or more in this study. Clinical, electrocardiographic, and ICD-stored data and electrograms were collected and analyzed.

Results

During the follow-up of 16.7 ± 10.6 months, 45 (28.5%) and 20 (12.6%) patients received first appropriate ICD therapy for VT and ventricular fibrillation, respectively. We divided the 45 patients with VT (based on the median value of VT cycle length) into 2 groups. Although patients with VT cycle length of less than 350 had higher total mean number of appropriate ICD therapy (25 vs 6.3, P = .023), during multivariate regression analysis, only left ventricular ejection fraction (EF) of less than 25% (P = .020) was correlated with total number of appropriate ICD therapy. First VT cycle length (P = .341), QRS duration (P = .126), age (P = .405), underlying heart disease (P = .310), indication of ICD implantation (P = .113), and sex (P = .886) have failed to predict the total burden of ventricular arrhythmia during the follow-up period.

Conclusion

After adjustment for left ventricular EF, initial VT cycle length per se did not confer a lower risk for subsequent ventricular arrhythmia recurrence compared with those with faster VT. Left ventricular EF of less than 25% was correlated with higher ventricular arrhythmia burden in patients with ICD.     

24-Hour QT variability in heart failure

Background

Previous studies have shown that increased temporal variability of repolarization, as reflected by QT interval variability measured for 10 minutes, predicted spontaneous ventricular arrhythmias in implantable cardioverter defribrillator patients, but it is unclear how these measures perform in 24-hour recordings.

Methods

Twenty-four-hour digital Holter recordings from 372 subjects with chronic heart failure enrolled in Gruppo Italiano per lo Studio della Sopravvivenza nell'Insufficienza Cardiaca, (GISSI) Heart Failure study were analyzed using a template-matching, semiautomatic algorithm to measure QT and heart rate time series in sequential 5-minute epochs for 24 hours. QT variability was expressed as normalized QT variance (QTVN) or as the log ratio of the QTVN over normalized heart rate variance (QT variability index, or QTVI).

Results

A pronounced diurnal variation was seen in both QTVI and QTVN. Both were lowest in the midnight to 6 am time frame and increased throughout the day, peaking at noon to 6 pm, then decreasing 6 pm to midnight. For QTVI, all 4 time points were significantly different (P < .0001). QT variability index correlated with heart rate (r = 0.38, P < .0001) and was significantly higher for those in higher New York Heart Association (NYHA) classes (r = 0.22, P = .0003). Normalized QT variance did not correlate with heart rate or NYHA but correlated negatively with serum potassium (r = −0.22, P = .0002) and manifested the greatest increase during midmorning hours.

Conclusions

Repolarization lability as reflected in QT variability has a pronounced diurnal variation and increases significantly after 6 am, the time of greatest arrhythmic risk. QT variability for 24 hours might improve risk prediction in chronic heart failure patients and should be tested in appropriate trials.     

Handheld ECG in analysis of arrhythmia and heart rate variability in children with Fontan circulation

Background

Our aim was to evaluate the intermittent use of a handheld ECG system for detecting silent arrhythmias and cardiac autonomic dysfunction in children with univentricular hearts.

Methods

Twenty-seven patients performed intermittent ECG recordings with handheld devices during a 14-day period. A manual arrhythmia analysis was performed. We analyzed heart rate variability (HRV) using scatter plots of all interbeat intervals (Poincaré plots) from the total observation period. Reference values of HRV indices were determined from Holter-ECGs in 41 healthy children.

Results

One asymptomatic patient had frequent ventricular extra systoles. Another patient had episodes with supraventricular tachycardia (with concomitant palpitations). Seven patients showed reduced HRV.

Conclusions

Asymptomatic arrhythmia was detected in one patient. The proposed method for pooling of intermittent recordings from handheld or similar devices may be used for detection of arrhythmias as well as for cardiac autonomic dysfunction.     

The rule of bigeminy revisited: analysis in sudden cardiac death syndrome

Background

The rule of bigeminy is commonly explained by a reentrant mechanism. We hypothesize that in patients with prolonged ventricular repolarization, the rule of bigeminy may be caused by premature ventricular complexes (PVCs) due to early afterdepolarizations. We evaluated these ventricular arrhythmias over extended periods in patients with sudden cardiac death syndrome.

Methods

The electrocardiographic (ECG) characteristics of 15 recordings from the PhysioNet Sudden Cardiac Death Holter Database were analyzed for the persistence of bigeminy, interaction between the underlying cardiac rhythm and the coupling interval, and influence of a prolonged initiating RR cycle on the self-perpetuation of the arrhythmias.

Results

Eight (53%) patients had classic torsade de pointes (TdP), 5 (33%) had other polymorphic ventricular tachycardia (VT), and 2 (13%) had monomorphic VT. Group A, which comprised 6 of the patients with TdP, had the following ECG tetrad: (1) frequent ventricular bigeminy (>5% of total ventricular arrhythmias), (2) long corrected QT interval (>0.5 second), (3) relatively fixed coupling interval, and (4) onset of bigeminy (n = 4) and TdP (n = 6) after a short-long RR sequence. Patients in group A had slower heart rates (mean RR = 1.12 ± 0.26 vs 0.77 ± 0.13 seconds, P < .01), longer QT intervals (corrected QT = 0.57 ± 0.06 vs 0.45 ± 0.06 second; P < .01) and more cases with prominent U waves (83% vs 33%, P < .05) than patients in group B (n = 9), composed of patients who had other types of VT, or TdP without frequent bigeminy.

Conclusions

We identified a set of ECG characteristics that supports the notion that premature ventricular complexes during self-perpetuating ventricular bigeminy (“rule of bigeminy”) in long QT syndromes may be due to early afterdepolarizations.     

Lability of R- and T-wave peaks in three-dimensional electrocardiograms in implantable cardioverter defibrillator patients with ventricular tachyarrhythmia during follow-up

Introduction

From experiments, we know that the heterogeneity of action potential duration and morphology is an important mechanism of ventricular tachyarrhythmia. Electrocardiogram (ECG) markers of repolarization lability are known; however, lability of depolarization has not been systematically studied. We propose a novel method for the assessment of variability of both depolarization and repolarization phases of the cardiac cycle.

Methods

Baseline orthogonal ECGs of 81 patients (mean ± SD age, 56 ± 13 years; 61 male [75%]) with structural heart disease and implanted single-chamber implantable cardioverter defibrillator (ICD) were analyzed. Clean 30-beat intervals with absence of premature beats were then selected. Baseline wandering was corrected before analysis. Peaks of R wave and peaks of T wave were detected for each beat, and the axis magnitude was calculated. The peaks were plotted to show clouds of peaks and then used to construct a convex hull, and the volumes of the R peaks cloud and T peaks cloud and ratio of volumes were calculated.

Results

During a mean (SD) follow-up period of 13 (10) months, 9 of the 81 patients had sustained ventricular tachycardia or ventricular fibrillation (VT/VF) and received appropriate ICD therapies. All ICD events were adjudicated by three independent electrophysiologists. There was no statistically significant difference in the volume of T-wave peaks or R-wave peaks between patients with and without VT or VF during follow-up; however, R/T peaks cloud volume ratio was significantly lower in patients with subsequent VT/VF (22.4 ± 25.4 versus 13.1 ± 7.9, P = .024).

Conclusions

Larger volume of T peaks cloud, measured during 30 beats of three-dimensional ECG, is associated with higher risk of sustained ventricular tachyarrhythmias and appropriate ICD therapies. New method to assess temporal variability of repolarization in three-dimensional ECGs by measuring volume of peak clouds shows potential for further exploration for VT/VF risk stratification.     

Predictive power of T-wave alternans and of ventricular gradient hysteresis for the occurrence of ventricular arrhythmias in primary prevention cardioverter-defibrillator patients

Background and purpose

Left ventricular ejection fraction lacks specificity to predict sudden cardiac death in heart failure. T-wave alternans (TWA; beat-to-beat T-wave instability, often measured during exercise) is deemed a promising noninvasive predictor of major cardiac arrhythmic event. Recently, it was demonstrated that TWA during recovery from exercise has additional predictive value. Another mechanism that potentially contributes to arrhythmogeneity is exercise-recovery hysteresis in action potential morphology distribution, which becomes apparent in the spatial ventricular gradient (SVG). In the current study, we investigated the performance of TWA amplitude (TWAA) during a complete exercise test and of exercise-recovery SVG hysteresis (SVGH) as predictors for lethal arrhythmias in a population of heart failure patients with cardioverter-defibrillators (ICDs) implanted for primary prevention.

Methods

We performed a case-control study with 34 primary prevention ICD patients, wherein 17 patients (cases) and 17 patients (controls) had no ventricular arrhythmia during follow-up. We computed, in electrocardiograms recorded during exercise tests, TWAA (maximum over the complete test) and the exercise-recovery hysteresis in the SVG. Statistical analyses were done by using the Student t test, Spearman rank correlation analysis, receiver operating characteristics analysis, and Kaplan-Meier analysis. Significant level was set at 5%.

Results

Both SVGH and TWAA differed significantly (P < .05) between cases (mean ± SD, SVGH: −18% ± 26%, TWAA: 80 ± 46 μV) and controls (SVGH: 5% ± 26%, TWAA: 49 ± 20 μV). Values of TWAA and SVGH showed no significant correlation in cases (r = −0.16, P = .56) and in controls (r = −0.28, P = .27). Receiver operating characteristics of SVGH (area under the curve = 0.734, P = .020) revealed that SVGH less than 14.8% discriminated cases and controls with 94.1% sensitivity and 41.2% specificity; hazard ratio was 3.34 (1.17-9.55). Receiver operating characteristics of TWA (area under the curve = 0.699, P = .048) revealed that TWAA greater than 32.5 μV discriminated cases and controls with 93.8% sensitivity and 23.5% specificity; hazard ratio was 2.07 (0.54-7.91).

Discussion and conclusion

Spatial ventricular gradient hysteresis bears predictive potential for arrhythmias in heart failure patients with an ICD for primary prevention, whereas TWA analysis seems to have lesser predictive value in our pilot group. Spatial ventricular gradient hysteresis is relatively robust for noise, and, as it rests on different electrophysiologic properties than TWA, it may convey additional information. Hence, joint analysis of TWA and SVGH may, possibly, improve the noninvasive identification of high-risk patients. Further research, in a large group of patients, is required and currently carried out by our group.     

Electrical restitution determined by epicardial contact mapping and surface electrocardiogram: its role in ventricular fibrillation inducibility in swine

Objective

The roles of electrical restitution determined by epicardial contact mapping and surface electrocardiogram (ECG) in the inducibility of ventricular fibrillation (VF) were evaluated.

Methods

Ten epicardial unipolar electrograms using contact mapping and the surface ECGs were simultaneously recorded in 7 swine. Activation-recovery interval (ARI) and QT-interval restitution curves were constructed. Steady-state pacing protocol was performed to induce VF. Ventricular fibrillation threshold was defined as the longest pacing interval for inducing VF. Statistical correlation analysis was performed to determine the relationship between local ARI restitutions, QT-interval restitution, and ventricular fibrillation threshold.

Results

One hundred thirteen restitution curves were constructed (50 in left ventricular sites, 52 in right ventricular sites, and 11 in surface ECG lead II) from 11 steady-state pacing procedures. Statistical correlation between the slopes of the QT restitution curve and the slopes of regional ARI restitution curves was noted in several mapping sites. Ventricular fibrillation threshold significantly related to the local ARI restitution curve slope for the right ventricular apex (R = 0.752, P = .019) and the QT-interval restitution curve slope (R = 0.802, P = .005).

Conclusion

There is a significant correlation between the local ARI restitutions and the QT-interval restitutions, both of which were associated with VF inducibility.     

Objective features of the surface electrocardiogram during ventricular tachyarrhythmias

The aim of this study was to quantify the electrocardiographicsignal characteristics of three types of ventricular arrhythmia;monomorphic ventricular tachycardia, polymorphic ventriculartachycardia and ventricular fibrillation. Patients in a coronarycare unit were monitored using a single bipolar ECG lead. Thirtyepisodes of ventricular tachyarrhythmia (ten from each group)were recorded automatically by computer. Frequency analysisof ten consecutive 1 s epochs from each recording gave 100 spectrafor each tachyarrhythmia group. Each spectrum was characterisedby the frequency, width and proportional size of the dominantpeak. Despite a qualitative similarity in spectral appearance,there were significant differrences in all characteristics betweenthe tachyarrhythmia groups (P<0·025). Ventricularfibrillation had a higher mean dominant frequency (4·8Hz) than polymorphic ventricular tachycardia (3·7 Hz)and monomorphic ventricular tachycardia (3·8 Hz). Thedominant frequency of ventricular fibrillation was also morevariable than that of monomorphic ventricular tachycardia (P<0·01).Mean peak size was largest for monomorphic ventricular tachycardia(0·78) and smallest for ventricular fibrillation (0·64).The single spectral peaks seen throughout this study indicatethat all three tachyarrhythmias have an underlying periodicmechanism. The difference in spectral characteristics show thatvarying degrees of myocardial electrical organisation can bequantified from surface ECG features.     

Long-term prognosis of inducible ventricular flutter: not an innocent finding

Background

The prognostic significance of ventricular flutter (VFL) induced during programmed electrical stimulation (PES) is currently unknown.

Methods

This study examined patients who had PES-induced VFL and assessed their long-term prognosis compared with patients who had inducible sustained monomorphic ventricular tachycardia (SMVT).

Results

Of 3414 patients undergoing PES, 74 (2%) had sustained VFL. They were compared with a group of 71 patients undergoing PES in the same time frame who had inducible SMVT. Patients with inducible VFL had a higher ejection fraction than patients with SMVT (0.39 vs 0.33; P = .05). More aggressive pacing was required for arrhythmia induction in patients with VFL, with more stimuli (2.7 ± 0.5 vs 2.2 ± 0.6; P <.01) and tighter S₂, S₃, and S₄ intervals. After a mean follow-up of 30 ± 31 months, the mortality rate was 34% in patients with VFL and 30% in patients with SMVT (P = .41). No difference in the 2 groups in overall survival or a combined end point of sudden death or appropriate implantable cardioverter defibrillator shock was revealed with Kaplan-Meier analysis.

Conclusion

The long-term prognosis of patients with inducible VFL is similar to that of patients with inducible SMVT, even when VFL is induced with a relatively aggressive protocol.     

Early sustained ventricular arrhythmias complicating acute myocardial infarction

Objective

Sustained ventricular arrhythmias complicate 2% to 20% of acute myocardial infarctions (MIs) and are associated with increased in-hospital mortality. However, it remains unclear whether successful mechanical revascularization improves outcomes in these patients. The objective of this analysis was to identify predictors of sustained ventricular arrhythmias after acute MI and to determine the influence of successful revascularization on in-hospital mortality.

Methods

We conducted a retrospective cohort study of all patients who underwent percutaneous coronary intervention for acute MI in New York State between 1997 and 1999.

Results

Of the 9015 patients who underwent percutaneous coronary intervention for acute MI, 472 (5.2%) developed sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) before revascularization. After multivariable adjustment, independent predictors of sustained VT/VF included cardiogenic shock (odds ratio [OR], 4.10; 95% confidence interval [CI], 3.20-5.58; P <.001), heart failure (OR, 2.86; 95% CI, 2.24-3.67: P <.001), chronic kidney disease (OR, 2.58; 95% CI, 1.27-5.23; P = .009), and presentation within 6 hours of symptom onset (OR, 1.46; 95% CI, 1.18-1.81; P = .001). Patients with sustained VT/VF had greater in-hospital mortality (16.3% vs 3.7%, P <.001). Although successful percutaneous coronary intervention was associated with decreased in-hospital mortality in patients with VT/VF (P <.001), patients with sustained VT/VF and successful revascularization experienced increased mortality compared with patients without sustained ventricular arrhythmias (P <.001).

Conclusion

Among patients undergoing percutaneous coronary intervention for acute MI, sustained VT/VF remains a significant complication associated with a 4-fold increased risk of in-hospital mortality. Early mortality is reduced after successful percutaneous coronary intervention, but remains elevated in this high-risk group.     

Heart rate turbulence and other autonomic risk markers for arrhythmia risk stratification in dilated cardiomyopathy

Background

Noninvasive arrhythmia risk stratification in patients with nonischemic dilated cardiomyopathy (DCM) using autonomic markers have yielded disappointing results. Heart rate turbulence is a new method to assess cardiac autonomic function.

Aim

The aim of the study was to compare the predictive value of heart rate turbulence with those of conventional autonomic risk markers for ventricular tachyarrhythmic events in patients with DCM.

Methods

The predictive value of heart rate turbulence, baroreflex sensitivity (phenylephrine method), and heart rate variability was assessed in patients with symptomatic congestive heart failure due to DCM who were in sinus rhythm and had a 24-hour Holter recording. Patients were followed for a combined end point of ventricular tachyarrhythmic events.

Results

A total of 114 patients (mean left ventricular ejection fraction, 28 ± 11%), included in the Frankfurt DCM database between 1996 and 2000, fulfilled the criteria for inclusion in this study. Determinate test results were obtained for heart rate variability in 98%, for baroreflex sensitivity in 90%, and for heart rate turbulence in 75% of patients (P = .008). Correlation between the different autonomic markers were only modest (r values, 0.36-0.43). During a follow-up of 22 ± 17 months, an end point event occurred in 15 patients. On univariate analysis, left ventricular ejection fraction and baroreflex sensitivity were significant predictors of arrhythmic events. On multivariate analysis, only baroreflex sensitivity remained an independent predictor (χ² = 3.17; P = .07).

Conclusion

Reliable analysis of heart rate turbulence is possible in approximately 75% of eligible patients with DCM. Whereas blunted baroreflex sensitivity is a predictor of arrhythmic events, heart rate variability and turbulence do not yield predictive power in these patients.     

Long-term prognosis of asymptomatic individuals with spontaneous or drug-induced type 1 electrocardiographic phenotype of Brugada syndrome

Background

Risk stratification of asymptomatic individuals with type 1 electrocardiogram (ECG) phenotype of Brugada syndrome (BS) still remains controversial. This study investigated the long-term prognosis of asymptomatic subjects with spontaneous or drug-induced type 1 ECG pattern of BS.

Methods and results

Data from 33 apparently healthy individuals (30 males; age, 43.6 ± 13.4 years) with spontaneous (n = 12) or drug-induced (n = 21) type 1 ECG pattern of BS were retrospectively analyzed. Thirteen subjects (39.4%) displayed a positive family history of BS and/or sudden cardiac death. Electrophysiologic study was performed in 16 subjects, and programed right ventricular stimulation induced polymorphic ventricular tachycardia in 9 (56.3%) of them. A cardioverter defibrillator was implanted in 6 cases. During a mean follow-up period of 5.3 ± 2.8 years, all subjects remained asymptomatic. None of them had syncope or cardioverter defibrillator discharges due to ventricular arrhythmias.

Conclusions

Asymptomatic individuals with spontaneous or drug-induced type 1 ECG phenotype of BS display a benign clinical course during long-term follow-up.     

Inducibility of sustained monomorphic ventricular tachycardia as a prognostic indicator in survivors of recent myocardial infarction: a prospective evaluation in relation to other prognostic variables

The prognostic significance of sustained monomorphic ventricular tachycardia inducible with up to three extrastimuli was assessed in relation to other prognostic markers, including clinical assessment, signal-average electrocardiogram (ECG), Holter monitoring, ejection fraction measurement and exercise testing, in 75 patients after recent myocardial infarction. Among eight patients with inducible sustained monomorphic ventricular tachycardia, six suffered arrhythmic events during a median follow-up period of 16 months. No patient without inducible sustained monomorphic ventricular tachycardia suffered an arrhythmic event. Multivariate analysis showed that of all the variables examined, inducible sustained monomorphic ventricular tachycardia was the only independent predictor of arrhythmic events during the follow-up period. The sensitivity for predicting arrhythmic events by this response was 100%, the specificity 97% and the positive predictive accuracy 75%. Individually, the other prognostic variables were less sensitive and much less accurate predictors of arrhythmic events, but the combination of the occurrence of acute phase complications or frequent ectopic activity with an abnormal signal-averaged ECG approached the sensitivity and accuracy of inducible sustained monomorphic ventricular tachycardia. The prognostic utility of programmed ventricular stimulation in patients with recent myocardial infarction is limited because comparable information can be obtained less invasively. However, the test may have a role in selecting therapy in patients judged to be at risk from arrhythmias on the basis of noninvasive assessment.     

Could sustained monomorphic ventricular tachycardia in the early phase of a prime acute myocardial infarction affect patient outcome?

Objectives

Sustained monomorphic ventricular tachycardia (SMVT) in the course of a prime acute myocardial infarction is not a common arrhythmia and its prognostic significance has not been specifically elucidated. The aim of the study was to estimate the prognostic implications of the occurrence of sustained monomorphic ventricular tachycardia in the early phase (<72 h) of a prime acute myocardial infarction.

Methods

We studied 690 consecutive patients admitted to the coronary care unit with a diagnosis of a prime myocardial infarction. SMVT was observed in 18 (2.6%) patients and we followed these patients for establishing the prognostic value of the arrhythmia according to the clinical characteristics.

Results

Patients with SMVT had a more extensive myocardial infarction based on the peak of the CK-MB isoenzyme activity (480±290 IU/L, vs 270±190 IU/L, P < .01), and higher mortality rate (40% vs 9%, P < .001). The independent predictors of SMVT were CK-MB (odds ratio [OR] 12.4), presence of complex ventricular arrhythmias (OR = 5.7), a wide QRS complex ≥130 milliseconds (OR = 4.8) and Killip class (OR = 4.8). The SMVT was itself an independent predictor of mortality (OR = 5.0). Compared with patients with ventricular fibrillation or polymorphic ventricular tachycardia, those with SMVT had a higher CK-MB activity, higher rate of wide QRS ≥130 milliseconds (33% vs 8%, P < .002), had a worse hemodynamic condition (Killip class >I:58% vs 23%, P < .04) and higher recurrence rate of ischemic events (68% vs 16%, P < .05). During the one year follow-up period, 4 patients (36.3%) of the 11 survivors from those with SMVT died of cardiac related causes.

Conclusions

SMVT during the first 72 h of a prime myocardial infarction is an index of a larger healing myocardium with acute very complexed electrophysiological changes and it is an independent predictor of in-hospital mortality and a prognostic factor of a poor one year outcome.     

Detection of asymptomatic arrhythmias in unexplained syncope

Background

Although electrocardiographic monitoring during syncope is the most unambiguous method of diagnosing or excluding an arrhythmia, it requires recurrence of syncope with potential morbidity. We hypothesized that long-term monitoring of patients with syncope would yield significant asymptomatic abnormalities that might preclude waiting for recurrence of actual syncope.

Methods

Sixty patients (age, 67±16 years; 27 men) with recurrent unexplained syncope, aged ≥30 years, with a left ventricular ejection fraction ≥35% and negative results on conventional monitoring were enrolled in a prospective study involving long-term automatic arrhythmia detection monitoring with an implantable loop recorder. Pre-specified significant asymptomatic arrhythmias were a pause >5 seconds, 3° atrioventricular block >10 seconds, heart rate (HR) <30 beats/min for >10 seconds while awake, wide complex tachycardia >10 beats, and narrow complex tachycardia >180 beats/min for >30 beats. Borderline asymptomatic arrhythmias included 3- to 5-second pauses, HR <30 beats/min for <10 seconds while awake, HR <30 beats/min for >10 seconds while asleep, and nonsustained wide complex tachycardia or narrow complex tachycardia.

Results

Recurrent symptoms developed in 30 patients during the 1-year follow-up period (47%), with arrhythmias detected in 14 patients (23%). Pre-specified significant asymptomatic arrhythmias developed in 9 patients (15%), with bradycardia in 7 patients who underwent pacemaker implantation. Twenty patients (33%) had borderline asymptomatic arrhythmias. Five of these patients (25%) went on to have more pronounced diagnostic arrhythmias of the same mechanism during further follow-up, including pauses of 6 to 17 seconds duration in 3 patients.

Conclusion

Long-term monitoring of patients with unexplained syncope with automatic arrhythmia detection demonstrated that significant asymptomatic arrhythmias were seen more frequently than anticipated, leading to a change in patient treatment. Automatic arrhythmia detection provides incremental diagnostic usefulness in long-term monitoring of patients with syncope.     

Comparison of 24-hour Holter Monitoring with 14-day Novel Adhesive Patch Electrocardiographic Monitoring

Background

Cardiac arrhythmias are remarkably common and routinely go undiagnosed because they are often transient and asymptomatic. Effective diagnosis and treatment can substantially reduce the morbidity and mortality associated with cardiac arrhythmias. The Zio Patch (iRhythm Technologies, Inc, San Francisco, Calif) is a novel, single-lead electrocardiographic (ECG), lightweight, Food and Drug Administration–cleared, continuously recording ambulatory adhesive patch monitor suitable for detecting cardiac arrhythmias in patients referred for ambulatory ECG monitoring.

Methods

A total of 146 patients referred for evaluation of cardiac arrhythmia underwent simultaneous ambulatory ECG recording with a conventional 24-hour Holter monitor and a 14-day adhesive patch monitor. The primary outcome of the study was to compare the detection arrhythmia events over total wear time for both devices. Arrhythmia events were defined as detection of any 1 of 6 arrhythmias, including supraventricular tachycardia, atrial fibrillation/flutter, pause greater than 3 seconds, atrioventricular block, ventricular tachycardia, or polymorphic ventricular tachycardia/ventricular fibrillation. McNemar's tests were used to compare the matched pairs of data from the Holter and the adhesive patch monitor.

Results

Over the total wear time of both devices, the adhesive patch monitor detected 96 arrhythmia events compared with 61 arrhythmia events by the Holter monitor (P < .001).

Conclusions

Over the total wear time of both devices, the adhesive patch monitor detected more events than the Holter monitor. Prolonged duration monitoring for detection of arrhythmia events using single-lead, less-obtrusive, adhesive-patch monitoring platforms could replace conventional Holter monitoring in patients referred for ambulatory ECG monitoring.     

fQRS as a marker of granulomatous disease in patients presenting with ventricular tachycardia and normal left ventricular ejection fraction

Background

Granulomatous myocarditis may present with sustained monomorphic ventricular tachycardia (SMVT) in the presence of normal left ventricular ejection fraction (LVEF), and could be mistaken for idiopathic ventricular tachycardia (IVT). The use of cardiac imaging for diagnosis can be limited by availability and high cost. ECG is readily available and inexpensive. Fragmented QRS (fQRS) on ECG has been found to be associated with myocardial scar. We hypothesized that fQRS could be useful in the diagnosis of granulomatous VT (GVT).

Methods

We compared the 12-lead ECG of 16 patients with GVT and 42 patients with IVT who presented with SMVT.

Results

The presence of fQRS was significantly higher in the GVT group compared to the IVT group (75% versus 19.1%, p < 0.001). The location of fQRS correlated with delayed enhancement cardiac magnetic resonance imaging (DE-CMR) in the same segment in 4/16 patients in the GVT group. It correlated with an affected segment on either DE-CMR or 18FDG positron emission computed tomography in 4/11 patients in the GVT group who had both imaging modality. Whenever fQRS was present in contiguous leads other than the inferior leads, it always corresponded to an affected segment on imaging.

Conclusions

In patients presenting with SMVT and no structural heart disease, the presence of fQRS is strongly associated with granulomatous myocarditis. fQRS on the surface ECG is a helpful tool the presence of which should prompt a CMR for a definitive diagnosis.     

Ventricular arrhythmias are not a short-term reproducible phenomenon – why long recording monitoring is necessary

Background

The variability of ventricular arrhythmias (VA) among different days of the week is not well detected by one-day Holter monitoring.

Aims

To evaluate whether there are differences in VA distribution pattern during long recording period.

Methods

The EKG was recorded for 14 h per day during 7 days by Holter system in 34 consecutive pat ventricular couplets and non-sustained ventricular tachycardia (NSVT) recording from patients provided graphic data. We applied the Hurst method (H Coefficient) which evaluates whether a repetitive phenomenon is random or not. When the H is > 0.5 and < 1 means it is not random and implies a long-term memory effect. Considering the arrhythmic variability, the data were also analyzed by repetitive ANOVA comparing incidence of arrhythmias among the days.

Results

Isolated PVCs and ventricular couplets during 98 h recording provided graphic of the occurrence. A trend of increasing and decreasing of arrhythmias was observed which looks erratic. The H coefficient, however, was significantly > 0.5 for all patients. Repeated ANOVA showed statistic difference among days in 31 patients with isolated PVCs; in 26 with ventricular couplets and 19 with NSVT when analyzed per hour during week days (p < 0.05).

Conclusion

PVCs, ventricular couplets and NSVT are not a random phenomenon. Our data suggest the occurrence of ventricular arrhythmias had no similarity among the days, making unlikely that a single Holter recording for 24 h may capture this phenomenon.