Cardiac troponin I levels are normal or minimally elevated after transthoracic cardioversion

Clinical Interpretation of Serum Troponin in the Era of High-Sensitivity Testing

Cardiac troponin (Tn) plays a central role in the evaluation of patients with angina presenting with acute coronary syndrome. The advent of high-sensitivity assays has improved the analytic sensitivity and precision of serum Tn measurement, but this advancement has come at the cost of poorer specificity. The role of clinical judgment is of heightened importance because, more so than ever, the interpretation of serum Tn elevation hinges on the careful integration of findings from electrocardiographic, echocardiographic, physical exam, interview, and other imaging and laboratory data to formulate a weighted differential diagnosis. A thorough understanding of the epidemiology, mechanisms, and prognostic implications of Tn elevations in each cardiac and non-cardiac etiology allows the clinician to better distinguish between presentations of myocardial ischemia and myocardial injury-an important discernment to make, as the treatment of acute coronary syndrome is vastly different from the workup and management of myocardial injury and should be directed at the underlying cause.

Maximum-fixed energy shocks for cardioverting atrial fibrillation

AIMS

Direct-current cardioversion is one of the most commonly performed procedures in cardiology. Low-escalating energy shocks are common practice but the optimal energy selection is unknown. We compared maximum-fixed and low-escalating energy shocks for cardioverting atrial fibrillation.

METHODS AND RESULTS

In a single-centre, single-blinded, randomized trial, we allocated elective atrial fibrillation patients to cardioversion using maximum-fixed (360-360-360 J) or low-escalating (125-150-200 J) biphasic truncated exponential shocks. The primary endpoint was sinus rhythm 1 min after cardioversion. Safety endpoints were any arrhythmia, myocardial injury, skin burns, and patient-reported pain after cardioversion. We randomized 276 patients, and baseline characteristics were well-balanced between groups (mean ± standard deviation age: 68 ± 9 years, male: 72%, atrial fibrillation duration >1 year: 30%). Sinus rhythm 1 min after cardioversion was achieved in 114 of 129 patients (88%) in the maximum-fixed energy group, and in 97 of 147 patients (66%) in the low-escalating energy group (between-group difference; 22 percentage points, 95% confidence interval 13-32, P < 0.001). Sinus rhythm after first shock occurred in 97 of 129 patients (75%) in the maximum-fixed energy group compared to 50 of 147 patients (34%) in the low-escalating energy group (between-group difference; 41 percentage points, 95% confidence interval 30-51). There was no significant difference between groups in any safety endpoint.

CONCLUSION

Maximum-fixed energy shocks were more effective compared with low-escalating energy shocks for cardioverting atrial fibrillation. We found no difference in any safety endpoint.

Therapeutic and Diagnostic Value of Caspase-12 and Study of Growth Differentiation Factor-15 in Patients with Acute Myocar-dial Infarction

Background:

To investigate the therapeutic and diagnostic value of caspase-12 and study of growth differentiation factor-15 (GDF-15) in patients with acute myocardial infarction (AMI).

Methods:

Overall, 78 patients with AMI admitted to Weifang People's Hospital Brain Hospital, Weifang, China from Apr 2016 to Apr 2019 were enrolled as AMI group. Seventy-five non-AMI people undergoing physical examination during the same period were enrolled as non-AMI group. The expression levels of caspase-12 and GDF-15 were detected and compared. The correlation between the expressions of GDF-15, caspase-12 and clinical characteristics and efficacy was detected. Single and combined detection of GDF-15 and caspase-12 were performed analyze their role in the early diagnosis, the prediction of efficacy, and the guidance of clinical therapy.

Results:

After treatment, the levels of GDF-15 and caspase-12 in AMI group were significantly lower than those before treatment (P<0.001). The expression levels of GDF-15 and caspase-12 were significantly correlated with blood pressure (P<0.05). The expression levels of GDF-15 and caspase-12 were significantly negatively correlated with clinical efficacy in AMI group. The diagnostic value of combined detection of GDF-15 and caspase-12 was higher than that of single diagnosis. The levels of serum caspase-12 and GDF-15 proteins were significantly up regulated in AMI patients. With the better therapeutic effect, the levels of serum caspase-12 and GDF-15 proteins decreased significantly.

Conclusion:

The levels of serum caspase-12 and GDF-15 proteins may be a key indicator in the clinical diagnosis of acute myocardial infarction and may be used to guide the treatment of AMI patients and predict the therapeutic efficacy.

Cardioversion of Atrial Fibrillation and Flutter: Comparative Study of Pulsed vs. Low Energy Biphasic Truncated Exponential Waveforms

Background

Despite the widespread use of biphasic waveforms for cardioversion and defibrillation, the efficacy and safety of shocks has only been compared in a few studies.

Methods

This retrospective study aims at comparing the efficacy and safety of biphasic truncated exponential (BTE) pulsed energy (PE) waveform with a BTE low energy (LE) waveform for cardioversion of atrial fibrillation (AF) and atrial flutter (AFL). The treatment energies were following an escalating protocol for PE waveform (120-200-200J in AF and 30-120-200J in AFL) and LE waveform (100-200-200J in AF and 30-100-200J in AFL). The protocol was stopped at successful cardioversion (sinus rhythm at 1 minute post-shock), otherwise after the 3rd shock. If the 3rd BTE shock failed, a monophasic shock of 360J was delivered.

Results

From May 2008 to November 2017, 193 patients (153 PE, 40 LE) were included in the study. Both groups significantly differed in a few characteristics, including chest circumference (p<0.05). After adjustment, the success rate was not significantly different for the two waveforms (94.5% PE vs 92.5% LE, Odds Ratio [95% Confidence Interval] = 0.25 [0.03-2.2]).There was no difference in safety: post-shock changes in Hsc-TnI levels were similar (p=0.25). The efficient cumulative energy was particularly related with BSA (β = 131.5, p=0.05), AF/AFL duration (β = 0.24, p=0.01) and gender (β = 61.8, p=0.05).

Conclusions

The major clinical implications of this study concern the high success rate of cardioversion with both biphasic pulses and no superiority of LE over PE waveform with an excellent safety profile without post-shock myocardial injuries.

Effects of hyperoxia on myocardial injury following cardioversion-A randomized clinical trial

Oxygen has long been assumed beneficial for all ill and injured patients. However, hyperoxia may be harmful and aggravate myocardial injury such as that caused by myocardial infarction. We aimed to investigate if hyperoxia increases myocardial injury following direct current cardioversion compared with room air.

METHODS

Patients undergoing elective biphasic cardioversion for atrial fibrillation or atrial flutter were randomized to receive room air or oxygen (10-15 L/min) during the procedure. The primary endpoint was the difference in high-sensitive Troponin I (hs-cTnI) and -T (hs-cTnT) measured 2 hours before and 4 hours after cardioversion. Secondary endpoints were differences in Copeptin and NT-pro-BNP.

RESULTS

A total of 65 patients were randomized to high-flow oxygen (male: 71%, mean age 66.9 years) and 59 patients to room air (male: 80%, mean age 65.5 years). There was no difference in hs-cTnI between patients treated with oxygen compared to patients treated with room air (P=.09) and no significant difference for hs-cTnT, ratio 1.08 (95% CI: 0.99-1.18) (P=.09). Median hs-cTnI difference before and after cardioversion was 0.1 (interquartile range (IQR): -0.5 to 0.5) ng/L for the high-flow oxygen group and -0.3 (IQR: -1.1 to 0.4) ng/L for the room air group. There was no difference in Copeptin between patients treated with oxygen compared to room air (ratio 1.06 (95% CI: 0.89-1.27) (P=.51) or NT-pro-BNP (difference-6.0 ng/L (95% CI: -78.5 to 66.6) P=.87).

CONCLUSION

Direct current cardioversion of atrial fibrillation/flutter with and without high-flow oxygen supplement was not associated with myocardial injury evaluated by high sensitive myocardial biomarkers.

Cardioversion Efficacy Using Pulsed Biphasic or Biphasic Truncated Exponential Waveforms: A Randomized Clinical Trial

Background

Several different defibrillators are currently used for cardioversion and defibrillation of cardiac arrhythmias. The efficacy of a novel pulsed biphasic (PB) waveform has not been compared to other biphasic waveforms. Accordingly, this study aims to compare the efficacy and safety of PB shocks with biphasic truncated exponential (BTE) shocks in patients undergoing cardioversion of atrial fibrillation or ‐flutter.

Methods and Results

This prospective, randomized study included patients admitted for elective direct current cardioversion. Patients were randomized to receive cardioversion using either PB or BTE shocks. We used escalating shocks until sinus rhythm was obtained or to a maximum of 4 shocks. Patients randomized to PB shocks received 90, 120, 150, and 200 J and patients randomized to BTE shocks received 100, 150, 200, and 250 J, as recommended by the manufacturers. In total, 69 patients (51%) received PB shocks and 65 patients (49%) BTE shocks. Successful cardioversion, defined as sinus rhythm 4 hours after cardioversion, was achieved in 43 patients (62%) using PB shocks and in 56 patients (86%) using BTE shocks; ratio 1.4 (95% CI 1.1–1.7) (P=0.002). There was no difference in safety (ie, myocardial injury judged by changes in high‐sensitive troponin I levels; ratio 1.1) (95% CI 1.0–1.3), P=0.15. The study was terminated prematurely because of an adverse event.

Conclusions

Cardioversion using a BTE waveform was more effective when compared with a PB waveform. There was no difference in safety between the 2 waveforms, as judged by changes in troponin I levels.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02317029.

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.

Cardiac Troponins in Dogs and Cats

Cardiac troponins are sensitive and specific markers of myocardial injury. The troponin concentration can be thought of as a quantitative measure of the degree of injury sustained by the heart, however, it provides no information on the cause of injury or the mechanism of troponin release. Conventionally, the cardiac troponins have been used for diagnosis of acute myocardial infarction in humans and have become the gold standard biomarkers for this indication. They have become increasingly recognized as an objective measure of cardiomyocyte status in both cardiac and noncardiac disease, supplying additional information to that provided by echocardiography and ECG. Injury to cardiomyocytes can occur through a variety of mechanisms with subsequent release of troponins. Independent of the underlying disease or the mechanism of troponin release, the presence of myocardial injury is associated with an increased risk of death. As increasingly sensitive assays are introduced, the frequent occurrence of myocardial injury is becoming apparent, and our understanding of its causes and importance is constantly evolving. Presently troponins are valuable for detecting a subgroup of patients with higher risk of death. Future research is needed to clarify whether troponins can serve as monitoring tools guiding treatment, whether administering more aggressive treatment to patients with evidence of myocardial injury is beneficial, and whether normalizing of troponin concentrations in patients presenting with evidence of myocardial injury is associated with reduced risk of death.

Troponin Marker for Acute Coronary Occlusion and Patient Outcome Following Cardiac Arrest

INTRODUCTION

The utility of troponin as a marker for acute coronary occlusion and patient outcome after out-of-hospital cardiac arrest (OHCA) is unclear. We sought to determine whether initial or peak troponin was associated with percutaneous coronary intervention (PCI), OHCA survival or neurological outcome.

METHODS

Single-center retrospective-cohort study of OHCA patients treated in a comprehensive clinical pathway from November 2007 to October 2012. Troponin I levels were acquired at presentation, four and eight hours after arrest, and then per physician discretion. Cardiac catheterization was at the cardiologist's discretion. Survival and outcome were determined at hospital discharge, with cerebral performance category score 1-2 defined as a good neurological outcome.

RESULTS

We enrolled 277 patients; 58% had a shockable rhythm, 44% survived, 41% good neurological outcome. Of the 107 (38%) patients who underwent cardiac catheterization, 30 (28%) had PCI. Initial ED troponin (median, ng/mL) was not different in patients requiring PCI vs no PCI (0.32 vs 0.09, p=0.06), although peak troponin was higher (4.19 versus 1.57, p=0.02). Of the 85 patients who underwent cardiac catheterization without STEMI (n=85), there was no difference in those who received PCI vs no PCI in initial troponin (0.22 vs 0.06, p=0.40) or peak troponin (2.58 vs 1.43, p=0.27). Regarding outcomes, there was no difference in initial troponin in survivors versus non-survivors (0.09 vs 0.22, p=0.11), or those with a good versus poor neurological outcome (0.09 vs 0.20, p=0.11). Likewise, there was no difference in peak troponin in survivors versus non-survivors (1.64 vs 1.23, p=0.07), or in those with a good versus poor neurological outcome (1.57 vs 1.26, p=0.14).

CONCLUSION

In our single-center patient cohort, peak troponin, but not initial troponin, was associated with higher likelihood of PCI, while neither initial nor peak troponin were associated with survival or neurological outcome in OHCA patients.

Successful Treatment of Refractory Electrical Storm With Landiolol After More Than 100 Electrical Defibrillations

Electrical storm (ES) was observed in an 82-year-old man with recent myocardial infarction. Conventional therapy, including amiodarone, could not suppress the ES. After more than 100 electrical defibrillations, we were finally able to control the ES with the administration of landiolol. It is known that landiolol can inhibit ES. However, we hesitate to use landiolol in patients with low cardiac output. We would like to emphasize that careful use of landiolol should be considered in patients with refractory ES after myocardial infarction, although cardiac output is severely reduced.

Myocardial injury secondary to ICD shocks: insights from patients with lead fracture

BACKGROUND

Patients who receive appropriate implantable cardioverter defibrillator (ICD) shocks have a subsequent adverse prognosis. Most data suggest that patients with inappropriate ICD shocks also have a subsequent adverse prognosis, although this is more controversial. The shocks may be an epiphenomenon, that is, a marker of underlying disease progression; however, it cannot be excluded that shocks cause direct myocardial damage. This latter question is difficult to clarify as the arrhythmia provoking the shock can also cause troponin release. Inappropriate shocks secondary to lead fracture are an ideal situation to examine this question; any troponin release in an otherwise well and hemodynamically stable patient, is likely due directly to the shocks.

METHODS

All patients with Fidelis lead fracture admitted to our institution with inappropriate shocks were included in this study. Troponin (I or T) was considered positive if the level was above the 99th percentile reference cutoff.

RESULTS

Elevated troponin levels were recorded in 16 of 22 patients (73%). Patients with elevated troponin received a higher number of shocks (20.3 ± 30.1 vs 5.3 ± 4.8, P = 0.07) compared with patients with normal troponin. Very elevated troponin levels (>0.8 mcg/L) were seen in five of 22 (22%) patients. The mean peak troponin level for these five patients was 7.06 ± 8.56 mcg/L; two patients had troponin levels that would be expected from a medium-sized myocardial infarction or severe myocarditis.

CONCLUSION

Troponin elevation occurred in the majority of our patients after inappropriate ICD discharges secondary to lead fracture. This indicates that ICD shocks can cause myocardial injury.

Circulating miRNAs: novel biomarkers of acute coronary syndrome?

Acute coronary syndrome refers to any group of clinical symptoms compatible with acute myocardial infarction (AMI). AMI is a major cause of death and disability worldwide with the greatest risk of death within the first hours of AMI onset. Therefore, delays in ‘ruling in’ AMI may increase morbidity and mortality due to the time lag in initiating therapy. Likewise, since the majority of patients presenting with acute chest pain do not have AMI, the rapid ‘ruling out’ of AMI in those patients would increase emergency department triage efficiency, decrease medical costs, and reduce morbidity and mortality. Thus, the identification of novel biomarkers that improve current strategies and/or accurately identify subjects who are at risk of developing acute and chronic manifestations of cardiovascular disease are desperately needed. This article discusses the potential of peripheral blood microRNAs as clinical biomarkers for the diagnosis and prognosis of cardiovascular diseases such as AMI.

MicroRNAs as biomarkers for myocardial infarction

MicroRNAs (miRs) are short non-coding RNA molecules involved in post-transcriptional gene regulation by binding to the 3' untranslated region of a messenger RNA (mRNA), thereby inhibiting the translation or inducing mRNA destabilization. MiRs are generally considered to act as intracellular mediators essential for normal cardiac function, and their deregulated expression profiles have been associated with cardiovascular diseases. Recent studies have revealed the existence of freely circulating miRs in human peripheral blood, which are present in a stable nature. This has raised the possibility that miRs may be released in the circulation and can serve as novel diagnostic markers for acute or chronic human disorders, including myocardial infarction (MI). This review summarizes the recent findings of miRs that fulfill the criteria of candidate biomarkers for MI.

Increases of cardiac troponin in conditions other than acute coronary syndrome and heart failure

BACKGROUND

Although cardiac troponin (cTn) is a cornerstone marker in the assessment and management of patients with acute coronary syndrome (ACS) and heart failure (HF), cTn is not diagnostically specific for any single myocardial disease process. This narrative review discusses increases in cTn that result from acute and chronic diseases, iatrogenic causes, and myocardial injury other than ACS and HF.

CONTENT

Increased cTn concentrations have been reported in cardiac, vascular, and respiratory disease and in association with infectious processes. In cases involving acute aortic dissection, cerebrovascular accident, treatment in an intensive care unit, and upper gastrointestinal bleeding, increased cTn predicts a longer time to diagnosis and treatment, increased length of hospital stay, and increased mortality. cTn increases are diagnostically and prognostically useful in patients with cardiac inflammatory diseases and in patients with respiratory disease; in respiratory disease cTn can help identify patients who would benefit from aggressive management. In chronic renal failure patients the diagnostic sensitivity of cTn for ACS is decreased, but cTn is prognostic for the development of cardiovascular disease. cTn also provides useful information when increases are attributable to various iatrogenic causes and blunt chest trauma.

SUMMARY

Information on the diagnostic and prognostic uses of cTn in conditions other than ACS and heart failure is accumulating. Although increased cTn in settings other than ACS or heart failure is frequently considered a clinical confounder, the astute physician must be able to interpret cTn as a dynamic marker of myocardial damage, using clinical acumen to determine the source and significance of any reported cTn increase.

Elevated serum cardiac troponin in non-acute coronary syndrome

Cardiac troponins (CTn) are the most sensitive and specific biochemical markers of myocardial injury and risk stratification. The assay for troponin T (cTnI) is standardized, and results obtained from different institutions are comparable. This is not the case with troponin I (cTnT), and clinicians should be aware that each institution must analyze and standardize its own results. Elevated cTn levels indicate cardiac injury, but do not define the mechanical injury. The differentiation of cTn elevation caused by coronary events from those not related to an acute coronary syndrome (ACS) is tiresome, at times vexing, and often costly. Elevation of cTn in non-ACS is a marker of increased cardiac and all-cause morbidity and mortality. The cause of these elevations may involve serious medical conditions that require meticulous diagnostic evaluation and aggressive therapy. At present, there are no guidelines to treat patients with elevated troponin levels and no coronary disease. The current strategy of treatment of patients with elevated troponin and non-ACS involves treating the underlying causes.

Present and Future Biochemical Markers for Detection of Acute Coronary Syndrome

The use of biochemical markers in the diagnosis and management of patients with acute coronary syndrome has increased continually in recent decades. The development of highly sensitive and cardiac-specific troponin assays has changed the view on diagnosis of myocardial infarction and also extended the role of biochemical markers of necrosis into risk stratification and guidance for treatment. The consensus definition of myocardial infarction places increased emphasis on cardiac marker testing, with cardiac troponin replacing creatine kinase MB as the "gold standard" for diagnosis of myocardial infarction. Along with advances in the use of more cardiac-specific markers of myocardial necrosis, biochemical markers that are involved in the progression of atherosclerotic plaques to the vulnerable state or that signal the presence of vulnerable plaques have recently been identified. These markers have variable abilities to predict the risk of an individual for acute coronary syndrome. The aim of this review is to provide an overview of the well-established markers of myocardial necrosis, with a special focus on cardiac troponin I, together with a summary of some of the potential future markers of inflammation, plaque instability, and ischemia.

Alteration in transthoracic impedance following cardiac surgery

INTRODUCTION

Haemodynamically significant ventricular tachyarrhythmias are a frequent complication in the immediate post-operative period after cardiac surgery. Successful cardioversion depends on delivery of sufficient current, which in turn is dependent on transthoracic impedance (TTI). However, it is uncertain if there is a change in TTI immediately following cardiac surgery using cardiopulmonary bypass (CPB).

METHODS

TTI was measured on 40 patients undergoing first time isolated cardiac surgery using CPB. TTI was recorded at 30 kHz using Bodystat Multiscan 5000 equipment before operation (with and without a positive end-expiratory pressure (PEEP) of 5 cm of H(2)O) and then at 1, 4 and 24 h after the operation. Data was analyzed to determine the relationship between pre- and post-operative variables and TTI values.

RESULTS

Mean pre-operative TTI was 54.5+/-10.55 ohms without PEEP and 61.8+/-15.4 ohms on a PEEP of 5 cm of H(2)O. TTI dropped significantly (p<0.001) after the operation to 47.2+/-10.6 ohms at 1 h, 42.6+/-10.2 ohms at 4 h and 41.8+/-10.4 ohms at 24 h. A positive correlation was noted between duration of operation and TTI change at 1 h (r=0.38; p=0.016). There was no significant correlation between the duration of bypass and change in TTI.

CONCLUSION

TTI decreases by more than 30% in the immediate post-operative period following cardiac surgery. This state may favour defibrillation at lower energy levels.

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.

Severe stunned myocardium after lightning strike

OBJECTIVE

To report the development of myocardial stunning and severe heart failure after lightning strike with total recovery of function.

DESIGN

Case report.

SETTING

Coronary care unit at Medica Sur Clinic, Mexico.

PATIENT

A 42-yr-old woman who was hit by lightning developed rapid and progressive hemodynamic deterioration manifested by cardiogenic shock that required invasive monitoring. Twenty-four hours after the strike, intravenous levosimendan and intra-aortic balloon pump were initiated because the patient demonstrated no significant response to management with conventional inotropic agents. Two days later, echocardiographic signs of systolic and diastolic dysfunction improved markedly. Dual-isotope-imaging myocardial perfusion testing with technetium-99m-sestamibi and thallium-201, performed 9 days after admission, showed normal perfusion and normal left ventricular systolic function. The patient exhibited complete recovery of function. The exact mechanism of abnormal contractility in the absence of direct electrofulguration is unknown but may be explained by release of oxygen free radicals, proteolysis of the contractile apparatus, and cytosolic overload of intracellular calcium, followed by reduced myofilament sensitivity to calcium. These abnormalities are consistent with stunned myocardium.

CONCLUSIONS

Lightning strike may cause serious contractile dysfunction in the absence of irreversible myocardial injury, but the exact mechanism of this phenomenon remains unknown. We propose that lighting strike can cause myocardial stunning resulting in severe but reversible left ventricular dysfunction. The patient's recovery was facilitated by support treatment including administration of levosimendan, which increases the intracellular sensitivity to calcium, a mechanism disturbed in patients with myocardial stunning.

Serum cardiac markers response to biphasic and monophasic electrical cardioversion for supraventricular tachyarrhythmia—a randomised study

BACKGROUND

Electrical cardioversion in patients with various types of supraventricular tachyarrhythmia (SVT) may induce serum cardiac markers elevation. Only a few studies have evaluated the impact of the type of shock waveform on electrical myocardial injury. The aim of our study was to compare the response of serum cardiac markers to biphasic and monophasic cardioversion for SVT.

METHODS

One hundred and forty one patients with various SVTs referred for electrical cardioversion were randomised to monophasic (MP) or biphasic (BP) cardioversion. Serum levels of creatine kinase (CK), MB fraction of CK (CK-MB), myoglobin and troponin I were analysed before cardioversion and 254+/-58 min after the procedure.

RESULTS

Average age of the patients was 67.9+/-11.3 years, 71 underwent BP and 70 MP cardioversion. In MP group, cumulative energy (CE)>150J was associated with significant elevation of CK and myoglobin levels after cardioversion (1.52+/-3.81 microkat/l and 187+/-433 microg/l), while CE<150J was not (-0.04+/-0.34 and 4+/-11, p<0.05). In BP group, CE>150J was associated with significant but smaller CK elevation (0.27+/-1.09 microkat/l, p<0.05) and comparable myoglobin elevation (80.7+/-21.4 microg/l, p<0.05). CE>150J was the only independent positive predictor for CK and myoglobin elevation in both groups. No significant changes in CK-MB and Troponin I levels after cardioversion were identified.

CONCLUSIONS

According to our study, electrical cardioversion for SVTs is not associated with biochemical signs of myocardial injury. Application of CE>150J can be followed by CK and myoglobin elevation most likely due to skeletal muscle damage. This reaction is more pronounced in MP than in BP cardioversion.

The influence of cardiopulmonary resuscitation without defibrillation on serum levels of cardiac enzymes: A time course study of out-of-hospital cardiac arrest survivors

BACKGROUND

The serum concentration of cardiac enzymes may be influenced by mechanical and electrical trauma due to cardiopulmonary resuscitation (CPR) attempts. This could complicate the determination of whether an acute myocardial infarction (AMI) had occurred. In this study, only patients without any of the known confounding factors affecting cardiac enzyme release were included, and the specific time course and patterns of serum cardiac enzyme levels after resuscitation were evaluated. The purpose is to help clinicians distinguish between spontaneous myocardial damage and that induced by CPR.

METHODS AND RESULTS

This prospective, observational study was performed in the emergency department on eight patients surviving cardiac arrest. They were selected for not having heart disease, chest trauma or septic shock; and not receiving defibrillation. The median (range) duration of return of spontaneous circulation (ROSC) was 13 min (5-30 min). Cardiac enzyme measurements were taken immediately after ROSC and every 6h thereafter. Although cardiac troponin I (cTnI) level reached as high as 62.6 ng/ml at 24 h in one patient, five of the eight (62.5%) patients had their cTnI level fall below the normal reference range (i.e. 2 ng/ml) by 30 h. The time to maximum and peak concentration of cTnI was 16.50+/-10.99 h and 16.85+/-21.50 ng/ml, respectively. Both MB creatine kinase (CKMB) and total creatine kinase (CK) levels were above their normal reference ranges. In addition, the CKMB/CK ratio exceeded 5% in all patients at any time point during this study.

CONCLUSION

In this study, the influence of resuscitative procedures - defibrillation excluded - on the release of cardiac enzymes were examined. During 30 h after ROSC cTnI level exhibited a bell-shaped configuration, which is distinct from that after AMI; whereas the enzymatic activities of CKMB and CK, as well as CKMB/CK ratio, were constantly higher than normal. This chronological pattern of cardiac enzyme levels may help physicians differentiate primary cardiac disease from other aetiologies in out-of-hospital cardiac arrests.

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.

Myocardial injury, neurohormonal activation and inflammation after internal atrial defibrillation

BACKGROUND

The effects of patient-activated atrial defibrillation on subclinical myocardial injury are unknown. Using biochemical markers, this study assessed the effect of a single internal atrial shock delivered by the implantable atrial defibrillator on myocardial damage, neurohormonal activation and inflammation.

METHODS

Twelve patients were implanted with a dual chamber defibrillator for the sole indication of drug refractory symptomatic persistent atrial fibrillation (AF). All had maximum defibrillation energy programmed to maximise the first shock success rate. Creatine kinase isoenzyme, troponin T, cortisol, catecholamines, C-reactive protein and brain natriuretic peptide were measured (i) during sinus rhythm, (ii) 8 h after onset of spontaneously occurring AF (before cardioversion) and (iii) 8 h following successful patient activated cardioversion.

RESULTS

There was no change in creatine kinase, troponin T, cortisol or C-reactive protein during AF or following internal cardioversion. Brain natriuretic peptide levels rose from a median value of 56 pg/ml during sinus rhythm (inter-quartile range 14-92 pg/ml) to 133 pg/ml during AF (30-262 pg/ml), p=0.002. There was a decrease 8 h after cardioversion to baseline (52 and 40-189 pg/ml), p=0.01. There were increases in serum adrenaline and noradrenaline levels during AF from 0.43 (0.12-0.61) to 0.58 pg/ml (0.39-0.80 pg/ml), p=0.002 and from 2.06 (1.61-2.59) to 2.83 nmol/l (2.43-3.46 nmol/l), p=0.02, respectively. These figures reverted to baseline levels 8 h post-cardioversion.

CONCLUSIONS

Internal atrial defibrillation does not result in myocardial injury. The onset of AF results in sympathetic activation and increased brain natriuretic peptide levels, which resolve following restoration of sinus rhythm.

Effects of transvenous pacing on cardiac troponin release

Cardiac troponins are invaluable tools for the detection of minimal myocardial injury. No study to date has analyzed the effect of permanent cardiac pacing on minimal myocardial injury detection by cardiac troponin I (cTnI) measurement. We investigated 76 clinically stable patients (mean age 75 years, range 31-93 years, 59% men) listed for elective endocardial permanent pacemaker insertion. Patients were required to have normal levels of cardiac cTnI, aspartate transaminase (AST) and creatinine kinase (CK) on a venous blood sample taken immediately prior to elective pacemaker implantation. Repeat measurements of AST, CK, and cTnI were performed at a mean of 19.2 post implantation. There was a detectable small rise in cTnI levels above normal in 21% of patients in a second blood sample taken 18-21 hours later (mean cTnI 0.39 +/- 0.37 microg/L, normal < 0.15 microg/L). The only factor that correlated with this rise was prolonged x ray screening time for lead implantation.

Serum Troponin I and Myoglobin After Monophasic versus Biphasic Transthoracic Shocks for Cardioversion of Persistent Atrial Fibrillation

This study compared the effects of standard monophasic versus biphasic direct current shocks for cardioversion of atrial fibrillation (AF) on the release of cardiac troponin I (cTnI) and myoglobin (Myo). We randomized 48 patients with persistent AF (mean age = 61.4 +/- 10.7 years, 33 men) to monophasic (45.2%) or biphasic (54.8%) cardioversion. Plasma concentrations of cTn1 and Myo were measured before, and 6 and 24 hours after the procedure. Cardioversion was significantly more effective (88% vs 100%, P < 0.04) and required less energy (348.1 +/- 254.1 vs 187.6 +/- 105.3 J; P < 0.001) in the biphasic than the monophasic group. A significant increase in mean plasma cTnI concentration over 24 hours (0.23 +/- 0.18 vs 0.41 +/- 0.37 ng/mL, P < 0.04), and mean Myo concentration were recorded in the monophasic group over the first 6 hours following the procedure (38.2 +/- 14.2 vs 221.9 +/- 51.3 ng/mL, P < 0.001), whereas no significant increase was observed in the biphasic group. Increases in cTnI and Myo in the monophasic group correlated closely with the cumulative energy delivered (Spearman correlation coefficient r = 0.58, P = 0.004 for Myo and r = 0.67, P < 0.001 for cTnI). In addition, there was a positive correlation between cumulative cardioversion energy load and increase in Myo and cTnI indexed with left ventricular mass (r = 0.45, P < 0.02 for Myo and r = 0.47, P = 0.01 for cTnI). It is concluded that in cardioversion of AF, biphasic are more effective than monophasic and may cause less myocardial injury.

Cardiac troponins in renal insufficiency and other non-ischemic cardiac conditions

The emergence of cardiac troponins has been an interesting step in the diagnosis of ACS. It has clearly helped us to better triage patients toward a more aggressive posture in performing early cardiac catheterization, and in some cases, early use of adjunctive Gp IIb/IIIa antagonists and percutaneous or surgical myocardial revascularization. However, with this step forward has come uncertainty and many cardiology consults regarding positive cardiac troponins in patients without ACS or myocardial infarction. In general, increased cardiac troponins imply a worse prognosis. This is clearly true of patients with ESRD and advanced heart failure. It is also true of patients with severe, noncardiac illnesses. In other situations, such as acute pericarditis and cardiac surgery, slightly elevated cardiac troponins do not seem to predict a worse prognosis, and can probably be disregarded. The elevation of cardiac troponins after successful percutaneous coronary interventions is not unexpected, and the level of cardiac troponin release seems to predict problems, but lively controversy persists. Last, monitoring cardiac troponins in cardiac transplant recipients and those receiving certain cardiotoxic chemotherapies may be of some diagnostic value, but clearly more experience and clinical research are needed.

Electrical cardioversion of atrial fibrillation

External direct current cardioversion remains the most common and effective method for restoration of normal sinus rhythm in patients with persistent AF. The development of biphasic defibrillators allows for higher success rates of conversion using standard energy levels. For persistent AF, an initial energy of 200 J is recommended for biphasic defibrillators, and 300 to 360 J are recommended for monophasic defibrillators, with the electrodes placed in the anterior posterior position. For refractory cases, alternatives are available such as dual defibrillators or internal cardioversion. Antiarrhythmic drugs may enhance the results of cardioversion by helping overcome shock failure or by preventing immediate recurrence of AF. Thromboembolism is the most important complication associated with cardioversion, but it can be prevented by providing 3 weeks of anticoagulation before the procedure or by excluding the presence of thrombi by transesophageal echocardiography, followed by an additional 4 weeks of anticoagulation.

Comparison of the efficacy and safety of two biphasic defibrillator waveforms for the conversion of atrial fibrillation to sinus rhythm

The overall efficacy of transthoracic biphasic shocks delivered for conversion of atrial fibrillation (AF) has been demonstrated. We compared 2 different energy waveforms, either the biphasic rectilinear (BRL) waveform or the biphasic truncated exponential (BTE) waveform, in the conversion of AF to sinus rhythm. The relation between energy required for the conversion of AF, the type of biphasic waveform, and patient characteristics were examined. Serum levels of cardiac troponin I were measured before and after cardioversion, as well as postprocedural skin erythema and discomfort. In this prospective trial, 101 patients (mean age 61 +/- 15 years, 72 men [71%]) referred for elective electrical cardioversion of AF were randomized to either a BTE or a BRL device. Shocks were delivered in a step-up fashion beginning with 50 J (then 100 J, 200 J, repeat 200 J, and then crossover to 360 J). One hundred patients were successfully converted to sinus rhythm (99% success rate). There was no difference in efficacy at any energy level used, regardless of the duration of the arrhythmia. In addition, there was no difference in cumulative success. Troponin I did not significantly increase after cardioversion, regardless of the total energy used. A positive correlation between skin erythema and skin discomfort after shock (24 to 48 hours) was seen with increasing cumulative energies. There was also a positive trend toward increasing energy requirements as chest circumference and body mass index increased. Thus, biphasic waveforms are safe and effective at converting AF to sinus rhythm. In this study population, there was no clinical difference between the BRL and the BTE waveforms.

Cardiac troponin I is increased after interventional closure of atrial septal defects

This study was designed to assess possible myocardial injury caused by interventional closure of atrial septal defects (ASDs) compared to diagnostic catheterization by measuring cardiac troponin I (cTn-I). Forty patients were enrolled; in 33 ASDs were successfully closed, while in 7 a diagnostic balloon sizing of the defect was performed only. Total cTn-I increased significantly from 0.1 to 1.9 microg/l at the end of the intervention and 2.23 at 4 hr and decreased to 1.35 at 15 hr. No significant increase could be detected in patients with diagnostic balloon sizing only or of CK/CK-MB levels either. Following interventional closure of ASDs with Amplatzer septum/PFO occluders, increased cTn-I levels for several hours indicate some transient, reversible myocardial membrane instability due to the device. Discrimination of ventricular myocardial infarction might be possible by estimating less sensitive CK and CK-MB levels only.

Cardiac troponin T and cardiac enzymes after external transthoracic cardioversion of ventricular arrhythmias in patients with coronary artery disease

BACKGROUND

Serum levels of cardiac troponins after external cardioversion (ECV) for atrial fibrillation and atrial flutter are widely investigated, and no increases in cardiac troponin T (cTnT) levels have been reported. However, the effect of ECV on cardiac enzyme release may depend on the type of arrhythmias. Furthermore, ventricular tachycardia (VT) or ventricular fibrillation (VF) could cause release of cardiac enzymes after ECV due to underlying myocardial ischemia, myocardial dysfunction, or more pronounced hemodynamic deterioration during arrhythmia.

AIM

The purpose of this study was to determine whether direct current (DC) shock may increase cardiac enzyme levels in patients with coronary artery disease undergoing ECV for VT or VF, so that diagnosis of acute myocardial infarction, which initially presents with VT or VF, can be excluded.

METHOD AND RESULTS

We obtained measurement of cTnT, total creatine kinase (CK), and CK MB isoenzyme (CK-MB) activity before and after ECV in 27 patients (mean +/- SD age, 62 +/- 13 years) with induced VT or VF (22 patients) who required ECV during provocative electrophysiologic testing and who underwent ECV due to VT (5 patients) in the cardiology department. Blood samples were drawn before, and 4 h, 8 h, and 24 h after ECV. The total energy used was 630 +/- 375 J (range, 200 to 1,280 J). CK levels rose to the upper limit of reference range in seven patients (26%), and CK-MB activity was higher than the normal reference range in five patients (19%) after ECV. In contrast, cTnT concentrations remained within the normal range (< 0.1 micro g/L) in all patients. Peak CK and CK-MB activity levels strongly correlated with the total energy delivered.

CONCLUSION

Elevation of cTnT level after an urgent DC shock strongly indicates the diagnosis of acute myocardial infarction presented with life-threatening arrhythmias, rather than myocardial damage caused by ECV.

Use of biphasic electrical cardioversion for treatment of idiopathic atrial fibrillation in two horses

Rectilinear biphasic cardioversion was used in 2 horses with idiopathic sustained atrial fibrillation; 1 horse converted to sustained sinus rhythm. Variables that potentially affected outcome of the electrical cardioversion procedures in these horses included duration of arrhythmia, placement of cardioverter pads and paddles, serum electrolyte concentrations, and treatment with quinidine. Serum cardiac troponin I concentration, measured to determine whether the myocardium was damaged from the electrical shocks, was within the reference range in both horses after the procedure. Biphasic electrical cardioversion may provide an alternative to pharmacologic cardioversion with quinidine in horses. The rectilinear biphasic defibrillator-cardioverter uses a unique biphasic waveform to deliver constant current to the myocardium during cardioversion, regardless of transthoracic impedance. Biphasic cardioversion is safer and more effective than traditional monophasic cardioversion in humans and animals.

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

INTRODUCTION AND OBJECTIVES

In this study we measured the concentrations of cardiac troponin I (cTnI) and several biochemical markers of myocardial damage after elective external cardioversion or internal cardioversion by specific catheters or automatic defibrillators.

MATERIAL AND METHODS

Biochemical markers were analyzed prospectively for 30 consecutive patients after electrical cardioversion. Concentrations of cTnI, myoglobin, creatine kinase (CK), CK-MB and the MB/CK ratio were determined in samples before cardioversion and 2, 8 and 24 h later. The shock energy ranged from 50 to 360 joules (235 106 joules) in external cardioversions and from 3 to 37 joules (15 8 joules) in internal cardioversions.

RESULTS

We detected abnormal concentrations of CK, myoglobin, CK-MB and MB/CK in 33% of the patients after external cardioversion. The concentrations of cTnI remained within normal limits at all times, with no elevations detected. Whereas no abnormal concentration of any biochemical marker was detected in any patient who required internal cardioversion for atrial fibrillation, two patients who underwent external cardioversion from an automatic defibrillator did have abnormal concentrations of CK-MB, myoglobin, and even of cTnI.

CONCLUSIONS

The concentration of cTnI remained below the detection limit after external cardioversion, even though the other more non-specific markers changed. No enzyme alteration was detected in patients who underwent internal cardioversion of atrial fibrillation.

Acute left ventricular failure after transcatheter closure of a secundum atrial septal defect in a patient with coronary artery disease: a critical reappraisal

We report a case of acute left ventricular failure after transcatheter closure of a single secundum atrial septal defect in a 68-year-old man with coronary artery disease. Just before the procedure, two coronary lesions had been treated with direct stenting. Transcatheter closure of atrial septal defects should always be deferred in ischemic heart disease patients who need percutaneous myocardial revascularization.

Atrial mechanical performance after internal and external cardioversion of atrial fibrillation: an echocardiographic study

OBJECTIVES

To compare the time course of resumption of mechanical performance of the left and right atrium after the novel method of internal low-energy cardioversion (CV) and conventional external CV of atrial fibrillation (AF).

BACKGROUND

Right atrial performance has been shown to normalize before the left atrium after external CV. However, no data on atrial function after internal CV are available.

PATIENTS AND INTERVENTIONS

Sixty-three patients with chronic AF were randomized to participate in either external or internal CV.

MEASUREMENTS

Echocardiographic examinations were carried out before as well as immediately after CV (day 0), and at days 1, 7, and 28 thereafter for the determination of cardiac dimensions, volumes, and transvalvular flow patterns.

RESULTS

After randomized internal CV or external CV, stable sinus rhythm was restored in 59 patients. Irrespective of the mode of CV, the right atrium resumed its mechanical function immediately after CV, whereas the left atrium was stunned beyond day 7. The mode of CV, internal or external, had no influence on the recovery of atrial mechanical function.

CONCLUSIONS

The right atrium resumes its normal function immediately after internal as well as external CV, whereas left atrium function is delayed. In contrast to the assumption that low-energy internal CV would impact less on atrial mechanical recovery, the type of method of CV used has no effect on such recovery.

Electrical storm presages nonsudden death: the antiarrhythmics versus implantable defibrillators (AVID) trial

BACKGROUND

Electrical storm, multiple temporally related episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF), is a frequent problem among recipients of implantable cardioverter defibrillators (ICDs). However, insufficient data exist regarding its prognostic significance.

METHODS AND RESULTS

This analysis includes 457 patients who received an ICD in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial and who were followed for 31 +/- 13 months. Electrical storm was defined as > or = 3 separate episodes of VT/VF within 24 hours. Characteristics and survival of patients surviving electrical storm (n = 90), those with VT/VF unrelated to electrical storm (n = 184), and the remaining patients (n = 183) were compared. The 3 groups differed in terms of ejection fraction, index arrhythmia, revascularization status, and baseline medication use. Survival was evaluated using time-dependent Cox modeling. Electrical storm occurred 9.2 +/- 11.5 months after ICD implantation, and most episodes (86%) were due to VT. Electrical storm was a significant risk factor for subsequent death, independent of ejection fraction and other prognostic variables (relative risk [RR], 2.4; 95% confidence interval [CI], 1.3 to 4.2; P = 0.003), but VT/VF unrelated to electrical storm was not (RR, 1.0; 95% CI, 0.6 to 1.7; P = 0.9). The risk of death was greatest 3 months after electrical storm (RR, 5.4; 95% Cl, 2.4 to 12.3; P = 0.0001) and diminished beyond this time (RR, 1.9; 95% CI, 1.0 to 3.6; P=0.04).

CONCLUSIONS

Electrical storm is an important, independent marker for subsequent death among ICD recipients, particularly in the first 3 months after its occurrence. However, the development of VT/VF unrelated to electrical storm does not seem to be associated with an increased risk of subsequent death.

Effects of Implantable Cardioverter Defibrillator Implantation and Shock Application on Biochemical Markers of Myocardial Damage

Background: Implantable cardioverter defibrillator (ICD) implantation is a common approach in patients at high risk of sudden cardiac death. To check for normal function, it is necessary to test the ICD. For this purpose, repetitive induction and termination of ventricular fibrillation by direct current shocks is required. This may lead to minor myocardial damage. Cardiac troponin T (cTnT) and I (cTnI) are specific markers for the detection of myocardial injury. Because these proteins usually are undetectable in healthy individuals, they are excellent markers for detecting minimal myocardial damage. The objective of this study was to evaluate the effect of defibrillation of induced ventricular fibrillation on markers of myocardial damage.

Methods: This study included 14 patients who underwent ICD implantation and intraoperative testing. We measured cTnT, cTnI, creatine kinase MB (CK-MB) mass, CK activity, and myoglobin before and at definite times after intraoperative shock application.

Results: Depending on the effectiveness of shocks and the energy applied, the cardiac-specific markers cTnT and cTnI, as well as CK-MB mass, showed a significant increase compared with the baseline value before testing and peaked for the most part 4 h after shock application. In contrast, the increases in CK activity and myoglobin were predominantly detectable in patients who received additional external shocks.

Conclusions: ICD implantation and testing leads to a short release of cardiac markers into the circulation. This release seems to be of cytoplasmic origin and depends on the number and effectiveness of the shocks applied.

Initial energy for elective external cardioversion of persistent atrial fibrillation

We conducted a prospective randomized study to determine the safety and efficacy rate of 3 commonly used energy levels (100, 200, and 360 J) for elective direct-current cardioversion of persistent atrial fibrillation. When compared with 100 and 200 J, the initial success rate with 360 J was significantly higher (14%, 39%, and 95%, respectively), and patients randomized to 360 J ultimately required less total energy and a lower number of shocks.

Evaluation of myocardial injury following repeated internal atrial shocks by monitoring serum cardiac troponin I levels

INTRODUCTION

Electrical shocks delivered for atrial cardioversion (CV) may cause myocardial damage. The aim of this study was to assess the extent of myocardial injury caused by repeated intracardiac shocks delivered for low-energy internal atrial CV.

METHODS AND RESULTS

Thirty-five patients with chronic persistent atrial fibrillation (AF) of different etiologies underwent CV with delivery of synchronized biphasic shocks (3.0/3.0 ms) between two catheters positioned in the right atrium and the coronary sinus. Shocks were delivered according to a step-up protocol (50 V, 180 V, then steps of 40 to 56 V up to 500 V, if necessary). In 23 patients, AF was reinduced after baseline CV, and CV was repeated. Myocardial injury was monitored by measuring cardiac troponin I (cTnI) serum concentrations in blood samples taken at baseline and at 2, 4, 8, 12, and 24 h after the procedure, by means of an immunoenzymologic assay (normal values, < or =0.6 ng/mL). A mean (+/- SD) of 6.9 +/- 3.4 shocks per patient were delivered (range, 2 to 17). Shocks delivered in each patient had a maximal energy of 7.3 +/- 4.0 J (range, 1.7 to 15.7). In 20 patients (57%), no evidence of myocardial injury (cTnI level, < or = 0.6 ng/mL) was found. In 13 patients (37%), mildly elevated cTnI levels (range, 0.7 to 1.4 ng/mL) in samples taken 4 to 12 h after CV suggested minor myocardial injury. In two patients (6%), higher cTnI levels were found in samples taken 4 to 8 h after CV (peak, 1.7 and 2.4 ng/mL), indicating a necrotic damage. Patients with no cTnI elevation, with mild cTnI elevation, or with cTnI levels >or =1.5 ng/mL did not differ significantly with respect to the total number of shocks delivered, the mean amount of energy delivered, and the cumulative amount of energy delivered. No clinical complications were observed.

CONCLUSIONS

Following internal CV with the delivery of repeated shocks, minor elevations of cTnI serum levels could be detected in a significant proportion of patients, and this suggests subtle asymptomatic minor myocardial injury. The elevations of cTnI levels do not appear to be related to the number of shocks or to the amount of energy delivered.