A middle-aged man with progressive fatigue

A DEFINITIVE DIAGNOSIS

5. Endomyocardial biopsy often provides the definitive diagnosis of cardiac sarcoidosis.

• True
• False

False. Endomyocardial biopsy often fails to reveal noncaseating granulomas, which have a patchy distribution.¹³ Table 2 summarizes the accuracy of tests for cardiac sarcoidosis.

Electrocardiography is abnormal in up to 50% of patients with sarcoidosis,²³ reflecting the conduction disease or arrhythmias commonly seen in cardiac involvement.

Chest radiography classically shows hilar lymphadenopathy and interstitial disease, and may show cardiomegaly, pericardial effusion, or left ventricular aneurysm.

Echocardiography is nonspecific for sarcoid disease, but granulomatous involvement and scar tissue of cardiac tissue may appear hyperechogenic, particularly in the ventricular septum or left ventricular free wall.²⁴

Angiography. Primary sarcoidosis rarely involves the coronary arteries,²⁵ so angiography is most useful in excluding the diagnosis of atherosclerotic coronary artery disease.

Radionuclide imaging with thallium 201 in patients with suspected cardiac sarcoidosis may be useful to suggest myocardial involvement and to exclude cardiac dysfunction secondary to coronary artery disease. Segmental areas with defective thallium 201 uptake correspond to fibrogranulomatous tissue. In resting images, the pattern may be similar to that seen in coronary artery disease. However, during exercise, perfusion defects increase in patients who have ischemia but actually decrease in those with cardiac sarcoidosis.²⁶

Nevertheless, some conclude that thallium scanning is too nonspecific for it to be used as a diagnostic or screening test.^27,28 The combined use of thallium 201 and gallium 67 may better detect cardiac sarcoidosis, as gallium is taken up in areas of active inflammation.

Positron-emission tomography (PET) with fluorodeoxyglucose F 18 (FDG), with the patient fasting, appears to be useful in detecting the early inflammation of cardiac sarcoidosis^29–34 and monitoring disease activity.^30,31 FDG is a glucose analogue that is taken up by granulomatous tissue in the myocardium.³⁴ The uptake in cardiac sarcoidosis is in a focal distribution.^30,31,34 The abnormal FDG uptake resolves with steroid treatment.^31,32

MRI has promise for diagnosing cardiac sarcoidosis. With gadolinium contrast, MRI has superior image resolution and can detect cardiac involvement early in its course.^{27,29,35–44}

Inflammation of the myocardium due to sarcoid involvement appears as focal zones of increased signal intensity on both T2-weighted and early gadolinium T1-weighted images. Late myocardial enhancement after gadolinium infusion is the most typical finding of cardiac sarcoidosis on MRI, and likely represents fibrogranulomatous tissue.²⁷ Delayed gadolinium enhancement is also seen in myocardial infarction but differs in its distribution.^1,35,45 Cardiac sarcoidosis most commonly affects the basal and lateral segments. In one study, the finding of delayed enhancement had a sensitivity of 100% and a specificity of 78%,^1,27 though it may not sufficiently differentiate active inflammation from scar.³⁰

Like FDG-PET, MRI has also been shown to be useful for monitoring treatment.^33,46 However, PET is more useful for follow-up in patients who receive a pacemaker or implantable cardioverter-defibrillator, in whom MRI is contraindicated. One case report²⁹ described using both delayed-enhancement MRI and FDG-PET to diagnose cardiac sarcoidosis.

TREATMENT

6. How is cardiac sarcoidosis currently treated?

• Implantable cardioverter-defibrillator
• Corticosteroids
• Heart transplantation
• All of the above
• None of the above

Corticosteroids

Corticosteroids are the mainstay of treatment of cardiac sarcoidosis, as they attenuate the characteristic inflammation and fibrosis of sarcoid granulomas. The goal is to prevent compromise of cardiac structure or function.⁴⁷ Although most of the supporting data are anecdotal, steroids have been shown to improve ventricular contractility,⁴⁸ arrhythmias,⁴⁹ and conduction abnormalities.⁵⁰ MRI and FDG-PET studies have shown cardiac lesions resolving after steroids were started.^31,45,46

The optimal dosage remains unknown. Initial doses of 30 to 60 mg daily, gradually tapered over 6 to 12 months to maintenance doses of 5 to 10 mg daily, have been effective.^45,51

Relapses are common and require vigilant monitoring.

Alternative agents such as cyclophosphamide (Cytoxan),⁵² methotrexate (Rheumatrex), ⁵³ and cyclosporine (Sandimmune)⁵⁴ can be given to patients whose disease does not respond to corticosteroids or who cannot tolerate their side effects.

Implantable cardioverter-defibrillator

Sudden death due to ventricular tachyarrhythmias or conduction block accounts for 30% to 65% of deaths in patients with cardiac sarcoidosis.¹⁰ The rates of recurrent ventricular tachycardia and sudden death are high, even with antiarrhythmic drug therapy.⁵⁵

Although experience with implantable cardiac defibrillators is limited in patients with cardiac sarcoidosis,^55–58 some have argued that they be strongly considered to prevent sudden cardiac death in this high-risk group.^57,58

Heart transplantation

The largest body of data on transplantation comes from the United Network for Organ Sharing database. In the 65 patients with cardiac sarcoidosis who underwent cardiac transplantation in the 18 years from October 1987 to September 2005, the 1-year post-transplant survival rate was 88%, which was better than in patients with all other diagnoses (85%). The 5-year survival rate was 80%.^59,60

Recurrence of sarcoidosis within the cardiac allograft and transmission of sarcoidosis from donor to recipient have both been documented after heart transplantation.^61,62