Cardiomegaly means enlargement of the heart. The definition is when the transverse diameter of the cardiac silhouette is greater than or equal to 50% of the transverse diameter of the chest (increased cardiothoracic ratio) on a posterior-anterior projection of a chest radiograph or a computed tomography. It should not be confused with an enlargement of the cardiomediastinal outline. Cardiomegaly is usually a manifestation of another pathologic process and presents with several forms of primary or acquired cardiomyopathies. It may involve enlargement of the right, left, or both ventricles or the atria.
Enlargement of the heart both in the form of dilatation or hypertrophy leads to a spectrum of clinical heart failure syndrome, with a prevalence of nearly 5.8 million people in the United States. Heart failure with preserved Ejection Fraction (HFpEF) represents more than half of these cases. The incidence of heart failure increases with age, male gender, and African American race. About half of the people diagnosed with heart failure die within 5 years of diagnosis.
The development of cardiac remodeling and hypertrophy is complex with genetic and non-genetic components. The most critical pathophysiological changes leading to cardiomegaly include dilated hypertrophy, fibrosis, and contractile malfunction. Contractile dysfunction and abnormal myocardial remodeling can lead to hypertrophic cardiomyopathy or dilated cardiomyopathy. Mechanical stretching, circulating neurohormones and oxidative stress are significant stimuli for the signal transduction of inflammatory cytokines and MAP kinase in cardiomyocytes. Signal transduction leads to changes in structural proteins and proteins that regulate excitation-contraction. Dilated cardiomyopathy mutations result in a reduced force of the sarcomere contraction and a reduction in sarcomere content. Hypertrophic cardiomyopathy mutations result in a molecular phenotype of hyperdynamic contractility, poor relaxation, and increased energy consumption.
Many patients with cardiomegaly are asymptomatic, and the presence of symptoms alone is neither sensitive nor specific to diagnosis. The diagnosis of cardiomegaly has its basis on imaging, and history is only helpful to determine the cause of heart failure symptoms which results in systemic congestion and impaired organ perfusion.
A detailed history should elicit the presence or absence of:
It is worth mentioning that cardiac function is adequate during rest may become inadequate with exertion. Hence it is not at all uncommon for patients to be asymptomatic at rest and experience symptoms on exertion only. The New York Heart Association classifies the severity of disease based on symptoms where class I disease is asymptomatic with ordinary physical activity and class IV denotes symptoms with rest.
Perhaps the most specific sign of cardiomegaly is a displaced point of maximal impulse (PMI). The precordial examination will reveal a displaced PMI usually below the 5th intercostal space and lateral to the midclavicular line and palpable across 2 intercostal spaces. Sustained PMI is a sign of severe left ventricular hypertrophy. A sustained and prolonged left parasternal heave is indicative of right ventricular hypertrophy. Another physical finding observed in cardiomegaly is the holosystolic murmur of mitral and/or tricuspid regurgitation resulting from dilatation of the mitral annulus and displacement of papillary muscles with abnormal myocardial remodeling. Other exam findings may be seen depending on the presence of decompensated heart failure. In such cases, a detailed physical exam may reveal the following abnormalities:
Diagnosis of cardiomegaly is primarily through imaging techniques that provide an assessment of the size and function of the heart. Diagnostic testing includes one of the following:
Treatment of mild cardiomegaly centers upon the treatment of the underlying condition. In moderate to severe cardiomegaly associated with heart failure, standard HF treatment guidelines also apply.
Of special consideration, no pharmacologic agent has shown benefit in HFpEF, and the mainstay of treatment is controlling underlying conditions such as hypertension, heart rate in patients with atrial fibrillation, ischemia with medication and/or coronary intervention, and diuretics for fluid overload. Patients with HOCM (hypertrophic obstructive cardiomyopathy) who are asymptomatic can be safely monitored. Patients who have symptoms of HF and left ventricular outflow tract obstruction, they may get benefit from negative inotropes such as beta blocker, calcium channel blocker or dipyridamole. Vasodilators and diuretics should be avoided in such patients.
Differentials of cardiomegaly include disorders that can result in an enlarged cardiomediastinal silhouette on a frontal (or posteroanterior) chest X-ray. These include:
Despite the advent of new therapies, mortality remains high in patients with symptomatic HF. Roughly, 1-year mortality is 30% while 5-year mortality is 50%. The severity of symptoms, advanced age, and HF hospitalization are significant predictors of mortality in HF.
Cardiac transplantation is an emerging treatment for patients with refractory end-stage heart failure. Patients undergo cardiopulmonary assessment and prognostication using specific scoring systems to determine their candidacy for transplant. Patients with systemic illness, life expectancy under 2 years, active substance and alcohol abuse, and non-compliance with medical therapy are considered poor candidates for cardiac transplantation. Patients should have a robust psychosocial support system to qualify. Ultimately, a risk-benefit assessment is necessary before the patient is a candidate for the transplant list. Patients who are not candidates for a cardiac transplant can qualify for a durable ventricular assist device.
Heart failure readmissions account for a majority of national healthcare expenditures. Support programs are operating nationwide to minimize the number of CHF related hospitalizations and thereby reduce the economic strain. These programs utilize a collaborative approach with many integrated disciplines and providers. Some of the inpatient strategies include guideline-based care, discharge support by nurses, patient education, medication reconciliation by the pharmacist, and early post-discharge follow up. A board-certified cardiology pharmacist can assist the clinicians in selecting medications for blood pressure control, as well as other factors where medication can provide ancillary benefit. Promising outpatient strategies include an interprofessional HF clinics and disease management programs that make in-person contact with patients and providing individualized education.
Cardiomegaly and HF require an interprofessional team approach that includes physicians and specialists, specialty-trained nurses, and pharmacists and therapists, all working collaboratively to bring about optimal therapeutic choices leading to the best possible patient outcomes. [Level V]
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