**5. Electrocardiogram findings**

Generally, the Electrocardiogram (ECG) is a sensitive means in myocarditis. However, its diagnostic value is limited by the low specificity and a wide diversity of changes which

Clinical Presentation 11

Several series have examined the frequency of myocarditis among patients evaluated for life threatening ventricular arrhythmias that occurred in the absence of structural heart disease (Strain et al., 1983; Sugrue et al., 1984; Vignola et al., 1984). These patients tended to be young (younger than 50 years) and to have normal or near-normal left ventricular systolic function. The frequency of syncope or cardiac arrest as reported has ranged from 8 percent to 61 percent (Strain et al., 1983; Sugrue et al., 1984). Biopsy evidence of myocarditis among patients without structural heart disease has ranged from 8 percent to 50 percent. On the other hand, patients with ventricular arrhythmias due to lymphocytic or granulomatous myocarditis stay at higher risk. Sustained ventricular tachycardia or new heart block in the setting of rapidly progressive congestive heart failure suggests giant cell myocarditis. Granulomatous myocarditis has been associated more frequently with life threatening ventricular arrhythmias, syncope, and high-grade atrioventricular block requiring temporary or permanent ventricular pacing than has lymphocytic myocarditis (Davidoff et al., 1991; Fleming & Bailey, 1981; Sekiguchi et al., 1996). Furthermore, granulomatous myocarditis might be suspected in patients who present with apparently chronic dilated cardiomyopathy yet with new ventricular arrhythmias or heart block or who do not have a

The risk of sudden dysrhythmic death in patients with myocarditis is increasingly appreciated in the current morbidity and mortality data. The discovery of myocarditis in 1 to 9 percent of routine postmortem examinations suggests that myocarditis is a major cause

Although heart failure and cardiomyopathy are more common clinical presentations, patients with myocarditis may present with syncope or unexpected sudden cardiac death, presumably due to ventricular tachycardia or fibrillation (Drory et al., 1991; Eckart et al., 2004; Maron et al., 2003; Theleman et al., 2001). Myocarditis is a significant cause of sudden, unexpected death in adults younger than age 40 years and elite young athletes. In these presumably healthy individuals, autopsy findings have revealed myocarditis in up to 20 percent of cases (Wesslen et al., 1996). In an autopsy series of patients under age 40 who presented with sudden death in the absence of known heart disease, myocarditis was responsible for 22 percent of cases under age 30 and 11 percent in older subjects (Drory et al., 1991). In another autopsy study of sudden death occurring in 1866competitive athletes, myocarditis was present in 6 percent of the cardiovascular deaths (Maron et al., 2009). In one more series of autopsies in military recruits, myocarditis accounted for 20 percent of deaths

A substantial subset of symptomatic cases of postviral or lymphocytic myocarditis present with a syndrome of heart failure and dilated cardiomyopathy. A clinical and pathologic syndrome that is similar to dilated cardiomyopathy (DCM) may develop after resolution of viral myocarditis in animal models and biopsy proven myocarditis in human subjects (Gilbert & Mason, 1987). This has led to speculation that DCM may develop in some individuals as a result of subclinical viral myocarditis. Theoretically, an episode of myocarditis could initiate a variety of autoimmune reactions that injure the myocardium and ultimately result in the development of DCM. These abnormalities in immune

response to optimal care (Yazaki et al., 1998).

of sudden, unexpected death (Feldman & McNamara, 2000).

due to identifiable structural cardiac abnormalities (Eckart et al., 2004).

**6.3 Sudden cardiac death** 

**6.4 Dilated cardiomyopathy** 

observed during the course of disease. The ECG must be timely repeated, since minor abnormalities detected initially may become subsequently more apparent.

The ECG findings associated with myocarditis may include first, second or third degree atrioventricular block, intraventricular conduction delay (widened QRS complex), bundle branch or fascicle block, reduced R wave height, abnormal Q waves, ST-T segment changes or low voltage. In one report, either ST-segment elevation or T-wave inversion is present as the most sensitive ECG criterion in <50% of patients, even during the first weeks of the disease (Morgera et al., 1992). A gradual increase in the width of the QRS complex may be a sign of exacerbation of myocarditis. Frequent premature beats, supraventricular tachycardia and atrial fibrillation may arise as well. Arrhythmias such as sinus arrest, ventricular tachycardia, ventricular fibrillation or asystole may occur and threaten the life of patients with myocarditis. Hence, continuous ECG monitoring is crucial to detect potentially fatal arrhythmias.
