Myocardial and Pericardial Disease: Difference between revisions

Nine different subgroups of secondary myocardial disease exist, which are defined as diseases of the myocardium with a known cause.

Myocardial disease with a known origin is termed secondary myocardial disease. Timely correction of the originating disease may result in reversal of the cardiomyopathy. Nine different etiologies can be distinguished:

* Hypertension

* Muscular dystrophy

Inadequately treated hypertension or aortic stenosis results in adaptation of the left ventricle by means of hypertrophy. Although primarily considered an adaptive process to systolic overload, hypertrophy of the left ventricle is associated with ventricular dysfunction, arrhythmias, and sudden cardiac death. The process of hypertrophy involves enlargement and proliferation of myocytes, and interstitial fibrosis characterized by deposition of collagen type I and III. With increasing fibrosis, the compliance of the ventricle decreases resulting in loss of diastolic function before systolic function is impaired. Within this process of increasing myocardial mass, the coronary vasculature fails to adapt accordingly. To compensate, the auto-regulatory mechanisms exhaust part of the coronary reserve by decreasing vascular resistance during resting conditions by vasodilation, to accommodate to the increase in myocardial oxygen demand. This renders the myocardium at high risk for ischemia, and hence, patients may suffer from anginal complaints even in the absence of significant coronary artery disease. In patients with LVH, atrial fibrillation and ventricular arrhythmias, including multifocal ventricular extrasystoles, and short runs of ventricular tachycardia, are frequently found. The combination of myocardial fibrosis, maladaptation of the vasculature causing ischemia, autonomic imbalance and a prolongation of the action potential may serve as arrhythmogenic substrate in patients with LVH, resulting in an increased risk of sudden cardiac death.

With regression of the ventricle, improved diastolic, and preserved systolic function result, as well as a relief of vascular maladaptation-induced ischemia. The combination of which results in a decrease in cardiovascular events.

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The group of metabolic cardiomyopathies comprises a heterogeneous group of myocardial disease secondary to a disruption in metabolism. Metabolic cardiomyopathy associated with diabetes mellitus is most common. Independent of its influence on hypertension or coronary artery disease, high levels of plasma glucose are increasingly associated with a direct deteriorative effect on ventricular function. Other examples consist of nutritional deficits such as thiamine deficiency, or storage diseases, and mutations in AMP kinase.

The prevalence of takotsubo cardiomyopathy is largely unknown, but the syndrome predominantly affects women between 60 and 65 years of age. Patients with Takotsubo cardiomyopathy present with electrocardiographic features mimicking an acute coronary syndrome in association with elevated cardiac biomarkers, but in the absence of significant coronary artery disease. The disease has inherited its name from the distinct angiographic feature of apical ballooning, resembling an octopus-pot or Tako-tsubo. Left ventricular function is typically impaired in the apical and mid ventricular regions, with preserved basal function, although reverse patterns may be seen. High levels of catecholamine have been suggested to play an important role in the etiology of the syndrome, which can be associated with emotional or physical stress, or in extremes in case of subarachnoidal haemorrhage. This catecholamine storm may induce severe peripheral coronary spasm, leading to its clinical presentation. Treatment usually consists of aspirin, ACE-inhibitors or angiotensin receptor antagonists in case of preserved blood pressure, beta-blockers to reduce heart rate, and nitrates to counteract coronary spasms. LV function may restore rapidly within a few hours or days, even when admission ejection fraction was severely impaired, and clinical outcome is good although the disease may recur in 5% of patients.

Left ventricular systolic function impairment within 1 month of delivery, or during the first 5 months post partum, in the absence of pre-existing cardiac disease, and in the absence of another recognized cause for the cardiac dysfunction is termed peripartum cardiomyopathy.

Despite optimal treatment, LV function may normalize in as less as 50% of patients, and may deteriorate to end-stage heart failure in 15%. Potential recurrence in future pregnancies requires counselling of patients to prevent subsequent episodes of symptomatic heart failure and progression of ventricular dysfunction.

Persistently high heart rates, such as in sustained ventricular tachycardia, or associated with atrial fibrillation, results in heart failure when left untreated. Normalization of the heart rate by means of beta-blockade subsequently leads to normalization of ventricular function, and is therefore the cornerstone in treatment of tachycardia-induced cardiomyopathy.

Defined as primary disorders of skeletal and/or cardiac muscles of genetic etiology, muscular dystrophies were primarily described based upon the distribution and extent of skeletal muscle involvement. The involvement of the heart was commonly attributed to processes extrinsic to the hearts, resulting in restrictive lung disease, subsequent pulmonary hypertension, and secondary myocardial dysfunction. Intrinsic dysfunction is increasingly recognized as an important etiology for myocardial function impairment in the presence of muscular dystrophy. Typical forms of dystrophy are based on deficiency of dystrophin, of which mutations have been described in X-linked DCM. Furthermore, histological changes were found in the myocardium similar to those in skeletal muscles, which suggest a common etiology, and cardiac manifestations may be present even in the absence of myopathic symptoms.

Treatment of cardiac dysfunction is treated according to the nature of cardiac involvement. Conduction disorders may present which require pacing, and standard heart failure therapy may be instituted in case of ventricular dilatation and functional impairment. Ventricular tachyarrhythmia may be found in particular in myotonic dystrophia, and require the implantation of an internal cardiac defibrillator to prevent its associated sudden cardiac death.