Utility of electrophysiological studies to predict arrhythmic events

AIM: To evaluate the prognostic value of electrophysiological stimulation (EPS) in the risk stratification for tachyarrhythmic events and sudden cardiac death (SCD).

METHODS: We conducted a prospective cohort study and analyzed the long-term follow-up of 265 consecutive patients who underwent programmed ventricular stimulation at the Luzerner Kantonsspital (Lucerne, Switzerland) between October 2003 and April 2012. Patients underwent EPS for SCD risk evaluation because of structural or functional heart disease and/or electrical conduction abnormality and/or after syncope/cardiac arrest. EPS was considered abnormal, if a sustained ventricular tachycardia (VT) was inducible. The primary endpoint of the study was SCD or, in implanted patients, adequate ICD-activation.

RESULTS: During EPS, sustained VT was induced in 125 patients (47.2%) and non-sustained VT in 60 patients (22.6%); in 80 patients (30.2%) no arrhythmia could be induced. In our cohort, 153 patients (57.7%) underwent ICD implantation after the EPS. During follow-up (mean duration 4.8 ± 2.3 years), a primary endpoint event occurred in 49 patients (18.5%). The area under the receiver operating characteristic curve (AUROC) was 0.593 (95%CI: 0.515-0.670) for a left ventricular ejection fraction (LVEF) < 35% and 0.636 (95%CI: 0.563-0.709) for inducible sustained VT during EPS. The AUROC of EPS was higher in the subgroup of patients with LVEF ≥ 35% (0.681, 95%CI: 0.578-0.785). Cox regression analysis showed that both, sustained VT during EPS (HR: 2.26, 95%CI: 1.22-4.19, P = 0.009) and LVEF < 35% (HR: 2.00, 95%CI: 1.13-3.54, P = 0.018) were independent predictors of primary endpoint events.

CONCLUSION: EPS provides a benefit in risk stratification for future tachyarrhythmic events and SCD and should especially be considered in patients with LVEF ≥ 35%.

Prediction of arrhythmic events by Wedensky modulation in patients with coronary artery disease

PRINCIPLES

Prediction of arrhythmic events (AEs) has gained importance with the availability of implantable cardioverter-defibrillators (ICDs), but is still imprecise. This study evaluated the innovative Wedensky modulation index (WMI) as predictor of AEs.

METHODS

In this prospective cohort, 179 patients with coronary artery disease (CAD) referred for AE risk assessment underwent baseline evaluation including measurement of R-/T-wave WMI (WMI(RT)) and left ventricular ejection fraction (LVEF). Two endpoints were assessed 3 years after the baseline evaluation: sudden cardiac death or appropriate ICD event (EP1) and any cardiac death or appropriate ICD event (EP2). Associations between baseline predictors (WMI(RT) and LVEF) and endpoints were evaluated in regression models.

RESULTS

Only three patients were lost to follow-up. EP1 and EP2 occurred in 24 and 27 patients, respectively. WMI(RT) (odds ratio [OR] per 1 point increase for EP1 20.1, 95% confidence interval [CI] 1.8-221.4, p = 0.014, and for EP2 73.3, 95% CI 6.6-817.7, p <0.001) and LVEF (OR per 1% increase for EP1 0.94, 95% CI 0.90-0.99, p = 0.013, and for EP2 0.93, 95% CI 0.89-0.97, p = 0.002) were significantly associated with both endpoints. In bivariable regression controlled for LVEF, WMI(RT) was independently associated with EP1 (p = 0.047) and EP2 (p = 0.007). The combination of WMI(RT) ≥0.60 and LVEF ≤30% resulted in a positive predictive value of 36% for EP1 and 50% for EP2.

CONCLUSIONS

WMI(RT) is a significant predictor of AEs independent of LVEF and has potential to improve AE risk prediction in CAD patients. However, WMI(RT) should be evaluated in larger and independent samples before recommendations for clinical routine can be made.

[Contemporary treatment of atrial flutter]

Atrial flutter is a relatively common arrhythmia that may be associated with substantial symptoms and morbidity. It can be harmful by impairing the cardiac output and by encouraging atrial thrombus formation that can lead to systemic embolization. In patients with atrial flutter four major issues that must be addressed. These are reversion to normal sinus rhythm, maintenance of sinus rhythm, control of the ventricular rate, and prevention of systemic thrombo-embolism. Nowadays, catheter ablation is the first line treatment of recurrent symptomatic or hemodynamically significant atrial flutter.

Impact of preload changes on positive and negative left ventricular dP/dt and systolic time intervals: preload changes on left ventricular function

AIM/OBJECTIVES

Previous work has shown that the electromechanical activation time (EMAT) is prolonged in patients with abnormally low left ventricular (LV) dP/dt. In the present study, we investigated whether EMAT was responsive to rapid changes in LV systolic function induced by abrupt increases in LV preload.

METHODS AND RESULTS

A total of 116 patients were assessed before and after LV angiography with a bolus injection of 40 mL of non-ionic contrast dye. Left ventricular end-diastolic pressure (LVEDP) increased from 18 ± 7 mmHg to 20 ± 8 mmHg (P < 0.01). In patients with a baseline dP/dt < 1500 mmHg/sec, dP/dt increased from 1098 ± 213 mmHg/sec to 1146 ±306 mmHg/sec (P=0.02) and EMAT decreased from 106 ± 29 ms to 103 ±18 ms (P=0.02). In patients with a baseline dP/dt > 1500 mmHg/sec, dP/dt decreased from 1894 ± 368 mmHg/sec to 1762 ± 403 mmHg/sec (P=0.01) and EMAT increased from 88 ± 13 ms to 93 ± 16 ms (P=0.02). Changes in negative dP/dt were similar to changes in dP/dt.

CONCLUSION

Electromechanical activation time is a non-invasively measured parameter that allows accurate and rapid detection of changes in LV contractility.

Impact of cardiac computed tomography of the interatrial septum before pulmonary vein isolation

BACKGROUND

Multidetector computed tomography (MDCT) may be useful to identify patients with patent foramen ovale (PFO). The aim of this study was to analyze whether a MDCT performed before pulmonary vein isolation reliably detects a PFO that may be used for access to the left atrium.

METHODS AND RESULTS

In 79 consecutive patients, who were referred for catheter ablation of symptomatic paroxysmal or persistent atrial fibrillation (AF), the presence of a PFO was explored by MDCT and transesophageal echocardiography (TEE). TEE was considered as the gold standard, and quality of TEE was good in all patients. In 16 patients (20.3%), MDCT could not be used for analysis because of artifacts, mainly because of AF. On TEE, a PFO was found in 15 (23.8%) of the 63 patients with usable MDCT. MDCT detected six PFO of which four were present on TEE. This corresponded to a sensitivity of 26.7%, a specificity of 95.8%, a negative predictive value of 80.7%, and a positive predictive value of 66.7%. The receiver operating characteristics curve of MDCT for the detection of PFO was 0.613 (95% confidence interval 0.493-0.732).

CONCLUSIONS

MDCT may detect a PFO before pulmonary isolation. However, presence of AF may lead to artifacts on MDCT impeding a meaningful analysis. Furthermore, in this study sensitivity and positive predictive value of MDCT were low and therefore MDCT was not a reliable screening tool for detection of PFO.

Effects of right ventricular pacing on left ventricular ejection fraction in a pacemaker clinic

BACKGROUND

The aim of this study was to evaluate whether a change of left ventricular ejection fraction (LVEF) depending on percentage of right ventricular pacing is found in a real-life setting of a pacemaker clinic.

METHODS AND RESULTS

269 patients with either a pacemaker or an ICD and who are regularly followed at the pacemaker clinic of the Luzerner Kantonsspital participated in the study. We tested whether LVEF measured by echocardiography between the first measurement at the time of the pacemaker implantation and the last measurement at the time of the last pacemaker control is dependent on the extent of ventricular pacing. Mean follow-up was 3.9 +/- 2.9 years. Mean LVEF most significantly decreased in the group of patients with baseline LVEF > or = 45% and an extent of right ventricular pacing > or = 66% (from 57.6 +/- 7.2% to 53.1 +/- 10.2%, P < 0.001). In patients with an extent of right ventricular pacing < 66% no decrease of LVEF was observed. Analysis of variance showed that LVEF decrease between the first measurement at the time of the pacemaker implantation and the last measurement at the time of the last pacemaker control was dependent on the extent of right ventricular pacing, even if other factors such as age, gender and previous myocardial infarction are incorporated in the analysis.

CONCLUSION

In a real-life population of a pacemaker clinic right ventricular pacing was associated with a decrease in LVEF.

Twelve-lead electrocardiography in the young: physiologic and pathologic abnormalities

BACKGROUND/ OBJECTIVE: The purpose of the present study was to analyze the prevalence of physiologic and pathologic ECG abnormalities in a cohort of young conscripts that represents the whole young generation of today.

METHODS

ECGs of all Swiss citizens who underwent conscription for the army during a 29-month period were analyzed manually.

RESULTS

ECGs of 43,401 conscripts (mean age 19.2 ± 1.1 years) were analyzed; 158 conscripts were female. Incomplete right bundle branch block was found in 5870 (13.5%) and left anterior fascicular block in 360 (0.83%). First-degree AV block was present in 329 (0.8%) and Mobitz type I (Wenckebach) second-degree AV block in 3 (0.01%). Early repolarization was observed in 1035 (2.4%), T-wave inversion in 39 (0.09%), and minor T-wave changes in 182 (0.42%). Brugada-like abnormalities were observed in 6 (0.01%). None of the conscripts had atrial fibrillation or flutter.

CONCLUSION

ECG abnormalities can be found in a relatively large proportion of young individuals. Incomplete right bundle branch block, left fascicular block, and first-degree AV block are the most frequent findings. No conscript presented with atrial fibrillation or flutter.

[Sport practice and arrhythmias]

Regular exercise decreases the risk of coronary artery disease by controlling risk factors. On the other hand, vigorous exertion increases the risk of sudden cardiac death in subjects with pre-existing cardiac diseases. Long term endurance sport practice may increase the incidence of atrial fibrillation, atrial flutter and sinus node dysfunction in otherwise healthy subjects.

Long-term follow-up of patients with isolated left ventricular noncompaction: role of electrocardiography in predicting poor outcome

BACKGROUND

Abnormal baseline electrocardiograms (ECGs) are common in patients with isolated left ventricular noncompaction (IVNC). Whether certain electrocardiographic parameters are associated with a poor clinical outcome, however, remains elusive. The present study was therefore designed to comprehensively assess the predictive value of baseline ECG findings in patients newly diagnosed with IVNC.

METHODS AND RESULTS

74 patients diagnosed with IVNC were included in the analysis. During follow-up, 8 patients (11%) died of a cardiovascular cause or underwent heart transplantation (primary outcome measure). On univariate analysis, several variables, including repolarization abnormalities (ST segment elevation/depression, T-wave inversion) in the inferior leads (5-year estimator: 67.1 ± 10.7% vs. 98 ± 2.2%; P = 0.001), an increase in PQ- (hazard ratio (HR) 1.032, P=0.004) and QTc-duration (HR 1.037, P=0.001), were predictive of cardiovascular death or heart transplantation. On multivariate analysis, only PQ- and QTc-duration and the presence of repolarization abnormalities in the inferior leads remained significantly predictive of a poor outcome.

CONCLUSIONS

PQ duration, QTc duration, and repolarization abnormalities in the inferior leads are independently predictive of a poor prognosis in IVNC. Further prospective studies are required to conclusively investigate the usefulness of baseline ECG parameters for risk stratification in patients with IVNC.

Noninvasive detection of left-ventricular systolic dysfunction by acoustic cardiography in atrial fibrillation

Objectives. Assessment of left ventricular (LV) systolic function in patients with atrial fibrillation can be difficult. Acoustic cardiography provides several parameters for quantifying LV systolic function. We evaluated the ability of acoustic cardiography to detect LV systolic dysfunction in patients with and without atrial fibrillation. Design. We studied 194 patients who underwent acoustic cardiography and cardiac catheterization including measurement of angiographic ejection fraction (EF) and maximum LV dP/dt. LV systolic dysfunction was defined as LV maximum dP/dt <1600 mmHg/s. Acoustic cardiographic parameters included electromechanical activation time (EMAT) and the systolic dysfunction index (SDI). Results. Acoustic cardiography detected systolic dysfunction with high specificity and moderate sensitivity with similar performance to EF (sensitivity/specificity without afib: EMAT 30/96, SDI 40/90, EF at 35% 30/96; sensitivity/specificity with afib: EMAT 64/82, SDI 59/100, EF at 35% 45/82). Conclusions. Acoustic cardiography can be used for diagnosis of LV systolic dysfunction in atrial fibrillation.

Progression of coronary artery disease during long-term follow-up of the Swiss Interventional Study on Silent Ischemia Type II (SWISSI II)

BACKGROUND

This study evaluates cardiovascular risk factors associated with progression of coronary artery disease (CAD) in patients with silent ischemia following myocardial infarction.

HYPOTHESIS

Coronary artery disease only progresses slowly with comprehensive risk factor intervention.

METHODS

A total of 104 of 201 patients (51.7%) of the Swiss Interventional Study on Silent Ischemia Type II (SWISSI II) with baseline and follow-up coronary angiography were included. All patients received comprehensive cardiovascular risk factor intervention according to study protocol. Logistic regression was used to evaluate associations between baseline cardiovascular risk factors and CAD progression.

RESULTS

The mean duration of follow-up was 10.3+/-2.4 years. At baseline, 77.9% of patients were smokers, 45.2% had hypertension, 73.1% had dyslipidemia, 7.7% had diabetes, and 48.1% had a family history of CAD. At last follow-up, only 27 patients of the initial 81 smokers still smoked, only 2.1% of the patients had uncontrolled hypertension, 10.6% of the patients had uncontrolled dyslipidemia, and 2.1% of the patients had uncontrolled diabetes. Coronary artery disease progression was found in up to 81 (77.9%) patients. Baseline diabetes and younger age were associated with increased odds of CAD progression. The time interval between baseline and follow-up angiography was also associated with CAD progression.

CONCLUSION

Coronary artery disease progression was highly prevalent in these patients despite comprehensive risk factor intervention. Further research is needed to optimize treatment of known risk factors and to identify other unknown and potentially modifiable risk factors.

Correlation relationship assessment between left ventricular hypertrophy voltage criteria and body mass index in 41,806 Swiss conscripts

INTRODUCTION

Electrocardiographic criteria for left ventricular hypertrophy (LVH) have been limited by low sensitivity at acceptable levels of specificity. A number of studies have demonstrated that body mass index (BMI) is associated with decreased sensitivity of ECG LVH classification in hypertensive patients. The objective of this study is to investigate the correlation relationship between LVH voltage criteria and BMI in Swiss conscripts.

METHODS

A database of 41,806 young Swiss people, who underwent compulsory conscription for the Swiss Army, was compiled. Along with other medical data, an ECG was taken. Statistical analyses, such as linear regression and calculation of correlation coefficient, were carried out between LVH voltage criteria and BMI.

RESULTS

The mean age in the studied population was 19.2 +/- 1.1 years with a median age of 19 years (range from 17 to 38 years). We found an overweight prevalence of 25.1%. The results showed that body habitus had significant association with Sokolow-Lyon voltages. A mean decrease of 13%, 5%, 19%, 14%, and 12% for the five studied Sokolow-Lyon indexes were found between normal range subjects (18.5 < or = BMI < 25) and obese subjects (25< or = BMI).

CONCLUSIONS

Our study confirms the hypothesis that people with higher BMI, a growing section of the population, have lower ECG amplitudes. Therefore, the Sokolow-Lyon voltage criteria may underestimate the presence of LVH for subjects with higher BMI, which is not the case for the Cornell voltage. Our analysis suggests that computerized electrocardiography for the diagnosis of left ventricular hypertrophy based on Sokolow-Lyon voltages should incorporate the BMI factor.

Electrocardiographic characteristics at initial diagnosis in patients with isolated left ventricular noncompaction

Isolated ventricular noncompaction (IVNC) is a primary cardiomyopathy characterized by a specific morphologic pattern. Patients with IVNC can develop various arrhythmic complications such as life-threatening ventricular arrhythmias, as well as heart failure or systemic embolic events. The present study was designed to comprehensively analyze the electrocardiographic (ECG) pattern at the initial diagnosis in patients with IVNC and to investigate their correlation with the clinical features and echocardiographic findings. Electrocardiograms from the initial diagnosis of IVNC were available for 78 patients from March 1995 to November 2008. The most common findings were intraventricular conduction delay (especially left bundle branch block), voltage signs of left ventricular (LV) hypertrophy, and repolarization abnormalities. An entirely normal electrocardiogram was present in 10 subjects (13%). However, no ECG findings or patterns specific for IVNC were found. A striking overlap was observed between the presence of intraventricular conduction delay (left bundle branch block, in particular), atrial conduction delay (PR interval prolongation or atrioventricular block), and prolongation of the QTc and reduced systolic LV function and LV/left atrial dilation. Moreover, patients with ECG voltage signs of LV hypertrophy more often presented with, or had a history of, systemic embolic events. In conclusion, our results have provided a comprehensive analysis of ECG findings of patients newly diagnosed with IVNC. Although intraventricular conduction delay, repolarization abnormalities, and LV hypertrophy are frequently present, no ECG patterns specific for IVNC at the first presentation with the disease were found. Whether these findings have prognostic implications needs to be investigated in long-term controlled studies.

Prevalence of long and short QT in a young population of 41,767 predominantly male Swiss conscripts

BACKGROUND

Abnormally long and short QT intervals are recognized to be associated with an increased risk for life-threatening ventricular arrhythmias. It is therefore important to define the upper and lower border of the normal QT.

OBJECTIVE

The aim of this study was to describe the normal distribution of the QT interval in a contemporary population of young conscripts and to define long and short limits of the QT interval.

METHODS

In Switzerland, all young male citizens must undergo compulsory conscription for the Swiss Army at the age of 18 to 19 years. In every conscript, an electrocardiogram (ECG) is performed. Retrospectively, 41,767 consecutive ECGs of Swiss citizens who underwent conscription for the army between March 1, 2004, and July 31, 2006, were analyzed.

RESULTS

The mean QTc Bazett interval was 394 +/- 22 ms. One percent of the conscripts had a Bazett QTc shorter than 347 ms, and one percent had a Bazett QTc longer than 445 ms, respectively. None of the subjects presented a QTc Bazett < 300 ms; the prevalence of a QTc Bazett < 320 ms was 0.02%.

CONCLUSION

The present study shows the distribution of QT intervals in an unselected young population. Because none of the subjects presented a QTc < 300 ms, it may be concluded that the short QT syndrome is a very rare entity in the population of young male adults.

Short-term effects of right ventricular pacing on cardiorespiratory function in patients with a biventricular pacemaker

The intention of this study was to evaluate the short-term effect of right ventricular (RV) pacing on cardiorespiratory function in patients with a biventricular pacemaker. A group of 26 patients with a biventricular pacemaker was enrolled in this cross-over, single-blind study. All patients underwent spiroergometry and electrocardiography in RV and biventricular pacing mode. Peak work capacity (102+/-32 W and 107+/-34 W for RV and biventricular pacing mode, respectively; P<.01) and peak oxygen consumption (21.4+/-6.7 mL/min/kg and 22.6+/-7.0 mL/min/kg for RV and biventricular pacing mode, respectively; P<.01) were significantly lower in the RV pacing mode. Heart rate at rest was significantly higher with active RV pacing. Short-term RV pacing in patients with a biventricular pacemaker resulted in a higher heart rate at rest, a lower peak work capacity, and a lower peak oxygen consumption compared with that in the biventricular pacing mode.