Dr. Eric Strong, internal medicine physician, faculty professor and YouTuber Strong Medicine, reviews the three categories of cardiomyopathy including their etiology, physiology, treatment, and what nurses need to look out for in patients with the disease. Dr. Strong will also explain why the term “cardiomyopathy” is surprisingly misleading and misunderstood by nurses and clinicians alike.
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What is cardiomyopathy, in laymans terms?
A disease in which the heart is not able to contract or relax well for some reason.
Current classifications:
- Hypertrophic
- Restrictive
- Dilated
A proposed change to classification
American Heart Association proposes the following classification of cardiomyopathies:
- Genetic
- Aquired
- Mixed
Currently, these terms are generally just used in academic cardiology.
Primary vs. Secondary CM
Primary CM: Disease is limited only to the heart, such as familial hypertrophic CM.
Secondary CM: A systemic disease that causes CM, such as restrictive CM caused by amyloidosis in which amyloid is deposited throughout the body.
Hypertrophic Cardiomyopathy (HCM)
Pathophysiology
- Hypertophy effects the intraventricular septum way out of proportion to the rest of the heart
- Exclusively a genetic diease
- LVH ≠ HCM
- Obstruction of outflow of LV, problematic during times of high cardiac output
- Potential for dysrhythmias such as VT and VF due to hypertrophy of the heart
Treatment for HCM
Low risk category:
- Avoid vigourous exercise
- Beta blockers decrease risk of fatal arrhythmia
- Periodic ECHOs and physical exams to monitor for progression of disease
High risk cateogy
The low risk category therapies PLUS
- AICD to shock out of fatal arrhythmia
- Remove part of excess myocardium alcohol ablation, surgerical myomectomy
Restrictive Cardiomyopathy (RCM)
Pathophysiology
Something has gotten into the myocardium that causes it not relax well such as
- Amyloidosis → amyloid
- Sarcoidosis → granulomas
- Hemochromatosis → iron
- Lymphoma → lymphoma cells
The inability of the ventricles to relax causes heart failure the preserved ejection fraction (HFpEF) although in later stages progress to heart failure with reduced ejection fraction (HFrEF)
Treatment
- Treatments are targeted based on the underlying cause of RCM
- Diuretics are used to reduce ventricular pressures, however look out for low cardiac output (there is a narrow therapeutic window)
- Look for symptoms of low cardiac output: brain fog, fatigue, post-prandial abdominal pain
Dilated Cardiomyopathy (DCM)
Pathophysiology
Large ventricular cavity causes poor contraction (systolic dysfunction), HFrEF. Presentation will include symptoms of low CO and venous congestion (pulmonary edema, lower extremity edema).
Causes
- Post-viral myocarditis ex: COX-B virus, HIV, Parvo virus
- Stress-induced ex: peripartum CM, Takatsubo CM
- Tachycardia induced ex: afib RVR
- Autoimmune: Immune response destroys myocytes ex: lupus, RA
- Toxins ex: Alcohol is toxic to myocytes; amphetamines cause microvascular damage that causes both reduced blood flow to myocytes and systemic hypertension
Treatment
Inpatient
Inpatient treatment is targeted at improving hemodynamics with diuretics, ACE inhibitors, hydralazine and nitrates.
Look for improvement with decreased edema, improved urine output and improved work of breathing.
Outpatient
Outpatient treatment is targeted at remodeling the heart (with neurohormal blockade), not hemodynamics (not targeting a specific BP).
Medications include beta-blockers, aldosterone antagonists (spirinaloctone) and neprilysin inhibitors (entresto)