[External and internal electrical cardioversion: comparative, prospective evaluation of cell damage by means of troponin I]

Evidence for Acute Myocardial and Skeletal Muscle Injury after Serial Transthoracic Shocks in Healthy Swine

Background

Previous serological studies have shown controversial results whether defibrillation or cardioversion can cause myocardial injury. Cardiovascular Magnetic Resonance (CMR) can be used to detect myocardial edema, hyperemia and capillary leak as features of acute myocardial injury. The aim of this study was to assess for myocardial and skeletal muscle injury in swine following transthoracic shocks.

Methods

Seventeen anaesthetized swine were examined, with 11 undergoing five synchronized transthoracic shocks (200J). Myocardial and skeletal muscle injury were assessed at baseline and up to 5h post-shock employing T1 mapping, T2 mapping, early and late gadolinium enhancement. Serologic markers (cFABP, TnI, CK, and CK-MB) and myocardial tissue were assessed by standard histology methods.

Results

In myocardial regions within the shock path, T1 and T2 were significantly increased compared to remote myocardium in the same animals. The early gadolinium enhancement ratio between the left-ventricular myocardium and the right pectoral muscle was also increased compared to control animals. After the shocks cFABP and CK were significantly elevated. After shock application, the regions identified as abnormal by CMR showed significantly increased interstitial and myocardial cell areas in histological analysis. This increased cell area suggests significant cellular and interstitial edema.

Conclusion

Our pilot study data indicate that serial defibrillator shocks lead to acute skeletal muscle and myocardial injury. CMR is a useful tool to detect and localize myocardial and skeletal muscle injury early after transthoracic shocks in vivo. In the future the technique could potentially be used as an additional tool for quality control such as verifying insufficient local shock application in non-responders after cardioversion or to develop safer shock forms.

Evaluating the Efficacy and Safety of Internal Cardioversion with Implantable Cardioverter Defibrillator Device for Atrial Fibrillation in Systolic Heart Failure Patients

BACKGROUND

Atrial fibrillation (AF) commonly observed in patients with heart failure and cardioversion was often needed to restore the sinus rhythm. Previously, there is no study evaluating usefulness of internal cardioversion with implantable cardioverter defibrillator (ICD) device. In this study, we aimed to compare the efficacy and long-term effects of internal cardioversion with ICD devices compared to conventional external cardioversion in patients with AF and heart failure.

METHODS

Seventy patients with AF and heart failure who underwent electrical cardioversion were enrolled in the study. Forty patients (mean age 65.36 ± 10.37, 35 male) were assigned to undergo internal cardioversion with approximately 35 J shocks delivered through the ICD electrode. Standard external cardioversion was performed for the remaining patients (30 patients; mean age 66.20 ± 11.89; 24 male) that were similar with regard to baseline, and electrocardiographic characteristics.

RESULTS

Sinus rhythm was restored in 32 of 40 patients (80.0%) assigned to internal cardioversion compared with 25 of 30 patients (83.3%) assigned to external cardioversion (P = 0.725). We did not witness any serious complication during the procedure and hospitalization. On the follow-up, there was no statistically significant difference in recurrence of AF and incidence of major cardiovascular events between the internal and external cardioversion groups.

CONCLUSIONS

Internal cardioversion with ICD device is an effective and safe method to restore sinus rhythm in heart failure patients with AF.

Troponin repercussion of defibrillation at the end of cardiopulmonary bypass

BACKGROUND AND AIM OF THE STUDY

Cardiopulmonary bypass (CPB) is a relatively common procedure in cardiac surgery. At the end, the heart is electrically defibrillated if not already beating. External and internal cardioversion by specific catheters do not raise plasma troponin concentration, but the possible repercussion on troponin of the direct cardioversion of the heart has not been documented.

METHODS

Prospective comparative trial in a surgical intensive care unit in a university hospital was conducted. The study sample comprised 364 consecutive patients undergoing cardiac surgery with CPB and without perioperative myocardial infarction.

RESULTS

The number of cardioversions applied was recorded and three groups were obtained: A/no cardioversion; B/one or two cardioversions; and C/more than two cardioversions. Serum troponin I and CK-MB were determined at admission and after 6, 12, 24, and 48 hours. Significant differences were found between group C and groups A and B for troponin I and creatine kinase (CK-MB) curves, being higher for both variables in group C.

CONCLUSIONS

With more than two cardioversions post-CPB, both troponin I and CK-MB may present an additional increase.

Serum troponin I level after external electrical direct current synchronized cardioversion in patients with normal or reduced ejection fraction: no evidence of myocytes injury

BACKGROUND

External electrical cardioversion (EEC) has been suggested as a cause of myocardial damage, but results from several previously published studies are conflicting.

HYPOTHESIS

The purpose of the study was to evaluate myocardial electrical injury caused by EEC.

METHODS

After elective EEC for atrial fibrillation (AF), cardiac troponin I (cTnI) was measured in 193 consecutive patients attending the Cardiology Department of the San Maurizio Hospital of Bolzano for elective EEC of AF over a period of 13 months. External electrical cardioversion was performed by one of the attending cardiologists with a synchronized monophasic defibrillator. Blood sample for cTnI was taken 18-20 h after EEC.

RESULTS

Of 193 patients, 183 (95%) were successfully cardioverted. Mean number of shocks was 1.46 and the mean total energy discharged per procedure was 379.4 +/- 229.2 J. Cardiac troponin remained under the limit of confidence for all patients with a mean value of 0.017 +/- 0.021 mcrg/l. No correlation between total energy delivered and cTnI was found. In the subgroup of patients with low ejection fraction, none had elevated cTnI, and no difference in cTnI values between these and patients with an ejection fraction > 40% was found.

CONCLUSIONS

The results of our analysis indicate that EEC caused no myocardial injury even in patients with low ejection fraction.