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What is the initial consequence of increased afterload due to high levels of Angiotensin II?
Which of the following complications can arise from mitral or tricuspid regurgitation in heart failure?
What clinical signs are most commonly associated with heart failure?
Which category of DCM etiology includes the effects of chronic alcohol ingestion?
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What is the significance of having a high annual mortality rate (10-50%) in heart failure patients?
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What is the primary impact of excessive alcohol use on cardiac function?
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What condition is often associated with chronic alcoholism that can be indistinguishable from DCM?
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What is a likely factor in the pathogenesis of peripartum cardiomyopathy?
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Which treatment is considered safest for managing arrhythmias in patients with poor left ventricular function?
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What is a common goal in the treatment of dilated cardiomyopathy?
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What percentage of patients with dilated cardiomyopathy spontaneously improve after diagnosis?
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Which condition is NOT typically regarded as a toxin that can lead to dilated cardiomyopathy?
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What is the estimated 5-year survival rate for patients with dilated cardiomyopathy without transplantation?
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What is the primary cause of symptoms in most patients with hypertrophic cardiomyopathy (HCM)?
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Which of the following is a major complication associated with hypertrophic cardiomyopathy?
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Which factor significantly correlates with the risk of sudden death in young athletes with hypertrophic cardiomyopathy?
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What leads to increased left ventricular (LV) pressure in patients with hypertrophic cardiomyopathy during exertion?
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What is one of the most common causes of sudden, unexplained death in young athletes as a result of hypertrophic cardiomyopathy?
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What is the most common cardiac abnormality in young athletes that can lead to sudden death during exertion?
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Which structural change in hypertrophic cardiomyopathy primarily affects diastolic filling?
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What is a hallmark histological finding in hypertrophic cardiomyopathy?
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In hypertrophic cardiomyopathy, what physiological issue arises due to the heavy and hypercontracting heart?
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Which of the following best describes the shape of the left ventricular (LV) lumen in hypertrophic cardiomyopathy?
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What ratio indicates asymmetric hypertrophy in hypertrophic cardiomyopathy?
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Which of the following mechanisms contributes to the myocardial ischemia in hypertrophic cardiomyopathy?
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What is the primary physiological function that is usually preserved in hypertrophic cardiomyopathy?
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What is the primary cause of left ventricular hypertrophy in hypertrophic cardiomyopathy?
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What sound is typically associated with left atrial contraction into a stiffened left ventricle in HCM patients?
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What condition is characterized by unexplained left ventricular hypertrophy in the absence of external stimuli?
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Which drug is considered standard therapy for managing symptoms in hypertrophic cardiomyopathy?
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What is the primary aim of serial echocardiograms in patients with HCM?
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Which condition is characterized by progressive fibrosis and rhythm disturbances primarily affecting the right ventricle?
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What is the likely consequence of outflow obstruction in a patient with HCM?
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Study Notes
Dilated Cardiomyopathy
- Patient may be asymptomatic early on, but eventually develops heart failure
- Angiotensin II increases systemic vascular resistance, leading to an afterload that is too high for the impaired left ventricle to pump against
- Aldosterone increases intravascular volume and end-diastolic volume, leading to fluid backup and pulmonary and systemic congestion
- Chronic elevations in aldosterone and angiotensin II leads to cardiac remodeling and fibrosis
- With heart enlargement, mitral and tricuspid regurgitation can occur, resulting in:
- Increased volume and pressure loads in atria leading to dilation and possible atrial fibrillation
- Regurgitation of blood into the left atrium further decreases forward stroke volume into the aorta and systemic circulation
- Regurgitant volume returns to the left ventricle during each diastole resulting in a greater volume load for the left ventricle to pump out
Dilated Cardiomyopathy: Clinical Features
- Slow, progressive signs and symptoms of congestive heart failure
- Cool extremities, low arterial pressure, tachycardia
- Pulmonary venous congestion leads to auscultatory crackles
- Left and upward displacement of the point of maximal impulse, enlarged heart
- Third heart sound (S3)
- Complications: Mitral/Tricuspid Regurgitation, atrial fibrillation, mural thrombus/thromboembolism
- High annual mortality rate: 10-50% die usually from progressive cardiac failure or arrhythmia
Dilated Cardiomyopathy: Etiology
- Most commonly idiopathic
- Familial/Genetic
- Inflammatory
- Infectious (Viral)
- Toxic
- Chronic alcohol ingestion
- Chronic cocaine use
- Chemotherapeutic agents
- Toxin-Induced
- Strong association with chronic excessive alcohol use
- Ethanol inhibits mitochondrial oxidative phosphorylation and fatty acid oxidation, leading to declining cell function
- Acetaldehyde, an alcohol metabolite, is a direct toxin to the myocardium
- Chronic alcoholism causes thiamine deficiency, leading to beriberi (beriberi heart disease is indistinguishable from DCM)
- Reversible with cessation of alcohol
- Strong association with chronic excessive alcohol use
- Other toxins: Adriamycin chemotherapy agents (Doxorubicin/Daunorubicin), cobalt, chronic cocaine use, iron overload (hemochromatosis)
### Dilated Cardiomyopathy: Peripartum Associated
- Can occur late in pregnancy or up to 6 months postpartum, is multifactorial in origin but poorly understood
- Possible reasons: immune response/cytokine release, pregnancy associated hypertension, volume overload, nutritional deficiencies
- Recent work suggests the primary defect is microvascular angiogenic imbalance in the myocardium leading to functional ischemic injury
- 50% regain normal ventricular function
- Risks include advanced maternal age, African American race, multiple pregnancies/gestations
- May have recurrence in future pregnancies
Dilated Cardiomyopathy: Treatment
- Goals: Treat early, treat underlying cause, provide symptom relief, decrease backward vascular congestion, increase forward cardiac output (CO), prevent complications, prevent thromboembolic events, prevent and treat ensuing arrhythmias, improve long term survival
- Standard CHF meds: Na+ restriction, ACEI/ARBs, beta blockers, diuretics, digoxin
- In those with poor left ventricular function, anti-arrhythmic drugs may worsen rhythm and lead to arrhythmias. Amiodarone is considered safest in these cases.
- Anticoagulation therapy may be needed for those prone to thrombus formation
- Implantable cardioverter-defibrillator (ICD)
- Cardiac transplant may be the only definitive treatment
- 1/3 patients spontaneously improve after diagnosis
- Without transplantation, 5 year survival is 74%; 10-year survival is 55%
Dilated Cardiomyopathy: Case
- A 58-year-old man presents with dyspnea on exertion and fatigue
- Physical exam shows evidence of congestive heart failure
- Echocardiogram discloses a dilated left ventricle with a left ventricular ejection fraction of 20%
- Liver appears fatty by MRI
- Cardiac catheterization demonstrates minimal coronary artery atherosclerosis
- Most likely cause of these signs and symptoms: Alcoholic cardiomyopathy
Hypertrophic Cardiomyopathy (HCM)
- Hypertrophic obstructive cardiomyopathy aka idiopathic hypertrophic subaortic stenosis, incidence 1 in 500 births worldwide
- Poorly compliant left ventricular myocardium leading to abnormal diastolic filling
- 25-33% have intermittent ventricular outflow obstruction, primarily due to issues with diastolic function, while systolic function is typically preserved
- Mechanisms of HCM:
- Left ventricular hypertrophy, which leads to increased muscle mass that the existing vasculature cannot support, decreased compliance and outflow obstruction, coronary arteries narrows due to wall hardening, leads to myocardial ischemia.
- Disease of sarcomere proteins, causing massive primary myocardial hypertrophy of ventricular wall without dilation
- Unexplained left ventricular hypertrophy in the absence of external stimuli (e.g., hypertension or aortic stenosis)
- Heart is thick-walled, heavy, and hypercontracting (vs flabby, hypocontracting heart of DCM)
- The most common cardiac abnormality in young athletes who die suddenly during exertion due to ventricular arrhythmia
HCM: Gross Pathology and Histology
- Asymmetric (not concentric) hypertrophy; septum to free wall thickness ratio ≥ 3:1 - subaortic septum most commonly affected
- Hypertrophy symmetric or asymmetric; asymmetric is more commonly seen and is found at the septum
- The left ventricle lumen has a “banana like” shape due to protrusion of the septum
- The left ventricular outflow tract often has a fibrous endocardial plaque due to thickening of the anterior mitral leaflet
- Chaotic arrangement of myocardial fibers makes the tissue stiff and leads to diastolic failure
HCM: Clinical Features
- Range from no limitations to extensive limitations on physical activity
- Most do NOT have severe outflow obstruction; most symptoms result from hypertrophy-induced impairment in diastolic filling.
- Major clinical problems/complications: Mitral regurgitation, atrial fibrillation with mural thrombus, cardiac failure, ventricular arrhythmias, syncope and sudden death
- One of the most common causes of sudden, unexplained death in young athletes is HCM, due to ventricular fibrillation on strenuous exertion.
- Risks: History of syncope, family history of sudden death, high risk mutations, extreme hypertrophy (left ventricle wall thickness correlates with risk)
HCM: Clinical Features: Hypertrophy, Obstruction, and Mechanism
- Dyspnea: Diastolic impairment leads to increased left ventricular, left atrial and pulmonary capillary wedge pressures
- Angina: Hypertrophy leads to increased muscle mass, leading to loss of atrial kick and the development of arrhythmias. This further impairs diastolic filling and worsens pulmonary congestion
- Syncope: May be caused by increased left ventricular pressure during obstruction and possible mitral regurgitation
- Syncope: Increased left ventricular pressure during systole, outflow block, decreased cardiac output, syncope
HCM: Physical Exam
- S4 heart sound (left atrial contraction against stiffened left ventricle)
- Outflow obstruction: Harsh systolic ejection murmur, crescendo, de-crescendo, caused by turbulent flow through the narrowed outflow tract; best heard at left lower sternal border
HCM: Screening
- Screening of first degree relatives
- Serial echocardiograms to note increases in hypertrophy during growth
- All HCM patients, even if asymptomatic, should be evaluated as they're at risk for sudden death
HCM: Treatment
- Most do well with medications that relax the heart
- Obstruction: Avoid strenuous exercise/competitive sports and drugs that decrease preload or increase the force of contraction.
- Standard therapy = beta blockers
- Non-dihydropyridine calcium channel blockers (verapamil)
- Antiarrhythmic drugs such as amiodarone
- Implantable Cardioverter Defibrillator (ICD): life-saving for patients at high risk of sudden cardiac death
- Surgery: Myomectomy (more proven to hold) or septal ablation with alcohol
HCM: Pathophysiology Summary
- Myocardial oxygen consumption (MVO2) = coronary blood flow x arteriovenous difference in O2 content
Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)
- Also known as Arrhythmogenic Right Ventricular Dysplasia
- Rare, progressive, mostly sporadic
- Some familial forms occur: autosomal dominant with variable penetrance - deletions of cell membrane desmosomal junctional proteins leading to loss of cell-to-cell adhesions between cardiac myocytes, fibrosis, or aberrant signaling between cells.
- Leads to right ventricular failure and rhythm disturbances, especially ventricular tachycardia
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Description
This quiz covers the pathophysiology and clinical features of dilated cardiomyopathy. Learn about the effects of angiotensin II and aldosterone on heart function, as well as complications such as mitral and tricuspid regurgitation. Ideal for students seeking to understand heart failure mechanisms and their implications.
