Adrenergic myocarditis
Synonyms and keywords: Neurogenic stunned myocardium, catecholamine induced cardiomyopathy, catecholamine mediated myocarditis, focal myocardial necrosis, norepinephrine myocarditis.

# Overview
Adrenergic myocarditis is a reversible phenomenon of  catecholamine mediated myocardial inflammation seen in pheochromocytoma.  Pheochromocytoma is a tumor of adrenal medulla which produces excess amount of catecholamines.  Wide spectrum of myocardial dysfunctions are present in pheochromocytoma which include acute myocardial infarction (both ST elevation and non ST elevation), cardiomyopathy, takotsubo cardiomyopathy, congestive heart failure, acute pulmonary edema and cardiac arrythmia.  Direct myocardial injury caused by catecholamines is the most popular theory among other suggested causes.

# Historical Perspective
Clinically significant myocarditis is rare in pheochromocytoma, however, studies have shown that 50% of patients with pheochromocytoma had evidence of acute myocarditis on autopsy.
Pheochromocytoma classically presents with episodic hypertension, sweating, tremors and palpitations, 12% of patients have cardiac symptoms as their initial manifestation.  For the first time in 1987, Mc-Ginley et al described catecholamine induced myocarditis as the presenting manifestation of pheochromocytoma.  In one study done by Sardesai etal five out of six patients with pheochromocytoma presented with acute pulmonary edema and died with in 24 hours.  Four out of those five patients had evidence of focal myocardial necrosis on autopsy.

# Pathophysiology
A number of mechanisms have been suggested to explain catecholamine mediated myocardial necrosis and inflammation:
- Direct toxic effect of catecholamines on cardiomyocytes mediated by Cycline adenosine monophosphate|cyclic-AMP results in increased calcium inside cells. This in turn impair their structure and function.
- Increased free radical production by catecholamines also contributes to cell damage.
- Vasospasm caused by catecholamines.

## Microscopic Features
Initially focal lesions of necrosis have edema and myofibril degeneration.  This initial necrosis results in inflammatory infiltration with monocytes. Histological changes include focal degeneration, contraction band necrosis, thickening of small and medium sized coronary arteries and interstitial fibrosis.

# Differentiating Adrenergic Cardiomyopathy from other Diseases

### Stress Cardiomyopathy
Stress cardiomyopathy, also known as Takotsubo cardiomyopathy, is a reversible cardiac condition where catecholamines involvement has been suggested to contribute to its pathophysiology. It occurs as a result of sudden emotional or physical stress.  Hypokinesia of the myocardial apex specifically results in apical ballooning of the myocardium.  Adrenergic myocarditis on the other hand can affect the myocardium focally as well as globally and does not show apical ballooning on echocardiography.

### Acute Coronary Syndrome
As acute coronary syndrome manifests very similarly to adrenergic myocarditis, it has to be ruled out with coronary angiography.  Adrenergic myocarditis lacks any evidence of coronary artery disease.

### Neurogenic Stunned Myocardium
Neurogenic stunned myocardium is also a type of myocardial hypokinesia which can occur in the setting of stroke and subarachnoid hemorrhage.  Catecholamines have been implied in its pathophysiology.

# Diagnosis

## History
The majority of pheochromocytoma patients present with a triad of headache, sweating and palpitations.  Weight loss, chest pain, blurring of vision and pallor are among other less common symptoms. Paroxysmal hypertension along with the presence of positive family history should raise suspicion of pheochromocytoma.

## Signs and symptoms
- Chest pain
- Chest tightness
- Breathlessness
- Dizziness
- Sweating

## Tests

### Cardiac Enzymes
Cardiac enzymes are elevated in adrenergic cardiomyopathy.  The cardiac enzymes normalize after resection of the tumor.

### Coronary angiography
As adrenergic myocarditis presents with symptoms similar to acute coronary syndrome, ACS has to be ruled out initially with coronary angiography.

### Echocardiography
Systolic anterior motion of mitral valve, global myocardial hypokinesia, hypokinesia of base and apex, and decreased ejection fraction are some of adrenergic myocarditis findings that can be detected by echocardiography.

### Electrocardiography
EKG of a patient suffering from adrenergic myocarditis can show left ventricular hypertrophy, sinus tachycardia, ischemic changes of myocardium and transient Q waves.

### Cardiovascular MRI
Cardiovascular MRI can be done to confirm echocardiography findings.

# Treatment
Surgical resection of the tumor is the ultimate treatment to remove excess catecholamines from the body.  Alpha receptors need to be blocked before surgery with phenoxybenzamine to control hypertension.