**6. Echocardiography**

Echocardiography looking for pericardial effusion and regional wall motion abnormalities is mandatory to help in making the diagnosis and excluding other serious differentials. Imazio

result in the reciprocal depressions in aVL that accompany inferior MI, although this may not apply in some cases of localized pericarditis [33]. The most specific EKG finding for acute pericarditis is PR segment depression (PR segment elevation in aVR) which is considered an early EKG marker in the evolution of acute pericarditis. PR segment depression is due to subepicardial atrial injury and is present in more than 60 % of the patients. Acute pericarditis causes characteristic EKG changes that typically evolve through

> - Widespread concave upward ST segment elevation except in leads aVR and V1


amplitude in lead V5 or V6 is ≥ 0.25





indefinitely (chronic pericarditis).




returns back to baseline.

even inverted

Nevertheless, perimyocarditis can present with focal instead of diffuse ST segment elevation mimicking transmural myocardial infarction. This, in addition to the presence of chest pain and elevated cardiac biomarkers can make the differentiation of increasing difficulty. This is important because fatal complications can occur if thrombolytic therapy is administered for a patient with acute pericarditis, or if a diagnosis of transmural myocardial infarction is missed. Omar et al. demonstrated a similar scenario where an EKG of a patient presenting with chest pain revealed focal ST segment elevation (figure 1) and the cardiac biomarkers were elevated mimicking STEMI. [34] Careful history taking, EKG interpretation and urgent

Previous studies have reported the use of thrombolytic therapy for what was later determined to be acute pericarditis [35, 36]. The utilization of urgent coronary angiography is not uncommon in patients with acute perimyocarditis. Salisbury and colleagues described the frequency of urgent coronary angiography in 238 patients with a final diagnosis of acute

Echocardiography looking for pericardial effusion and regional wall motion abnormalities is mandatory to help in making the diagnosis and excluding other serious differentials. Imazio

4 stages as demonstrated in table 2.

**Stage 1** Occurs during the first few days of pericardial

up to 2 weeks

**Stage 2** Occurs hours to days after

**Stage 3** Begins between the second

**Stage 4** May last from days up to 3

weeks

months

pericarditis to be 16.8 % [37].

**6. Echocardiography** 

inflammation and may last

initial symptoms and may last from days to several

and third week and may continue for several weeks

Table 2. The 4 Electrocardiographic stages of acute pericarditis.

echocardiogram favored the diagnosis of acute perimyocarditis.

Fig. 1. Concave upward ST segment elevation in leads II, III, Avf, V5 and V6 in a patient with perimyocarditis. Notice the focal pattern of ST segment elevation (inferolateral leads) thereby mimicking transmural myocardial infarction. Adapted from Omar et. al. [34].

and collegues found that pericardial effusions are present in approximately 60% of cases of acute pericarditis, with 80% being mild, 10% being moderate, and 10% being severe [26]. Pericardial effusion was present in 38.1% of patients in the ST segment elevation group and 73.5% of the patients in the non ST segment elevation and was explained by the tendency of the larger pericardial effusions to decrease voltage including the magnitude of ST segment elevation [26]. The presence of regional wall motion abnormalities favors an ischemic process rather than acute pericarditis. Another potential echocardiographic finding in perimyocarditis is transient myocardial thickening (figure 2 and 3) which is due to interstitial edema and its presence likely predicts a poor prognosis as it has been associated with a fulminant course [38]. In a series of 25 patients with acute myocarditis who underwent echocardiogram and endomyocardial biopsy, a significant decrease in myocardial thickness was observed between the acute and the convalescent phase. The reduction of the edema shown by the biopsy was also significant [39].

Fig. 2. Echocardiogram on admission. Parasternal long axis view (A) and short axis (B) in diastole. There is an asymmetrical thickening of the posterior wall involving the posterior papillary muscle, and slight pericardial effusion. Adapted from reference number 38 with permission.

Perimyocarditis 111

Fig. 4. Four chamber view (left). TRO study demonstrating mild-to-moderate pericardial effusion surrounding the heart. Left anterior oblique view (right) optimized to visualize the full length of the RCA. PE - pericardial effusion, RV - right ventricle, LV - left ventricle, LAD - left anterior descending coronary artery. Adapted with modification from reference

inammation. As it stays out of the vessel, it cannot be washed away and is held for a longer

time allowing it to be seen in the delayed enhancement images (figure 5) [44].

Fig. 5. Four chamber long-axis views. (A) Cardiac magnetic gadolinium delayed

enhancement showing subepicardial hyperenhancement (arrow). (B) Cardiac CT delayed enhancement (arrows). Adapted from reference 44 with permission from Elsevier.

Cardiac magnetic resonance can also be a tool to differentiate between acute perimyocarditis and myocardial infarction. In acute myocarditis, myocardial late gadolinium enhancement is present in up to 88% of cases [45,46] which characteristically has patchy distribution not conforming to any particular coronary artery territory and is usually in the subepicardial and not the subendocardial layer [47] differentiating it from

number 41 with permission.

myocardial infarction.

Fig. 3. Echocardiogram 5 days after admission. Parasternal long axis view (A) and short axis (B) in diastole. Normalization of the myocardial thickness in the posterior wall and posterior papillary and resolution of the pericardial effusion can be seen. Adapted from reference 38 with permission.
