Cardiomyopathies

Question 1

Some defined conditions that are associated with dilated cardiomyoapthy

Answer 1

• Viral myocarditis
• Chronic excessive alcohol ingestion
• Peripartum state
• Certain genetic mutations

Question 2

Major viruses that cause acute viral myocarditis

Answer 2

• Coxsackievirus Group B
• Parvovirus B19
• Adenovirus

Question 3

It appears as though viral myocarditis is a result of. . .

Answer 3

. . . fibrosis-inducing hypersensitivity to viral components rather than viral infection of the myocardium.

Question 4

Alcoholic cardiomyopathy is ___.

Answer 4

Alcoholic cardiomyopathy is reversible!

If the patient ceases drinking alcohol, symptoms will slowly disappear.

Question 5

Peripartum cardiomyopathy risk factors

Answer 5

• Between last month of pregnancy and 6 months postpartum
• Older maternal age
• African American heritage
• Having had multiple pregnancies
• Certain genetic risk factors

Question 6

Dilated cardiomyopathy is characterized by ___.

Answer 6

Dilated cardiomyopathy is characterized by marked enlargement of all four cardiac chambers by eccentric hypertrophy. (although sometimes it can be limited to L or R heart chambers)

Question 7

Pathophysiology of dilated cardiomyopathy

Answer 7

Ventricles dilate and contractile function declines. Frank-Starling mechanism, neurohormonal activation, and renin-angiotensin-aldosterone buffer at first, but as in heart failure the latter two have detrimental chronic effects on afterload. Angiotensin II also increases fibrosis rate.

Rapid enlargement causes AV valve failure and regurgitation. Valve failure further decreases stroke volume and may precipitate atrial fibrillation

Question 8

Clinical manifestations of DCM

Answer 8

Mostly the same as those of congestive heart failure.

Low forward output: Fatigue, lightheadedness, exertional dyspnea

Low backwards throughput: Pulmonary congestion, dyspnea, orthopnea, paroxysmal nocturanl dyspnea

Chronic systemic congestion: Edema, ascites

Question 9

Basic physical exam findings of low cardiac output

Answer 9

1. Cool extremities
2. Low arterial pressure
3. Tachycardia

Question 10

Signs of RV failure

Answer 10

• Systemic congestion (jugular vein distention, hepatomegaly, ascites, peripheral edema)
• Tricuspid valve murmur

Question 11

Diagnostic studies for dilated cardiomyopathy

Answer 11

• Chest radiograph
• ECG
• Echo
• Cardiac cath (sometimes w/ biopsy sample)
• Cardiac MRI

Question 12

Treating dilated cardiomyopathy

Answer 12

• Salt restriction
• Diuretics
• ACE inhibitor or ARB
• Beta blocker
• Spironolactone (potassium-sparing diuretic) for advanced heart failure
• Anticoagulative therapy to patients with severe depression of ventricular function, atrial fibrillation, previous thromboembolic event, or known intracardiac thrombus

Question 13

Preventing arrhythmias

Answer 13

1. Maintain serum eletrolytes in normal ranges (especially while on diuretic!)
2. Available antiarrhythmic drugs are actually contraindicated, they have been shown to worsen outcomes. This isn’t the setting they were designed for.
   
   • Exception is amiodarone, which reduces symptoms but is not associated with any change in mortality
3. Cardioverter-defibrillator has been shown to prevent deaths in DCM patients
4. Cardiac resynchronization therapy

Question 14

40% of advanced dilated cardiomyopathy patients die of ___.

Answer 14

40% of advanced dilated cardiomyopathy patients die of an arrhythmia that complicates their disease.

Question 15

Dilated cardiomyopathy patients are at increased risk for ___.

Answer 15

Dilated cardiomyopathy patients are at increased risk for thromboembolism.

Question 16

Hypertrophic cardiomyopathy notoriety in lay public

Answer 16

Hypertrophic cardiomyopathy (HCM) has received notoriety in the lay press because it is the most common cardiac abnormality found in young athletes who die suddenly during vigorous physical exertion.

Question 17

Hypertrophic cardiomyopathy is characterized by . . .

Answer 17

. . . asymmetric (or sometimes global) left ventricular hypertrophy that is not caused by chronic pressure overload. Systolic LV contractile function is vigorous but the thickened muscle is stiff, resulting in impaired ventricular relaxation and high diastolic pressures.

Question 18

Hypertrophic cardiomyopathy is a ___ disease.

Answer 18

Hypertrophic cardiomyopathy is a Mendelian disease.

It follows autosomal dominant inheritance with variable penetrance. Many different genes are implicated (myosin heavy chain (β-MHC), cardiac troponins, and myosin-binding protein C). The incorporation of these mutated peptides into the sarcomere is thought to cause impaired contractile function

Question 19

Answer 19

Image of a heart from an autopsy of a hypertrophic cardiomyopathy patient.

Note the thickness of the interventricular septum

Question 20

Histology of hypertrophic cardiomyopathy

Answer 20

The myocardial fibers are in a pattern of extensive disarray. Short, wide, hypertrophied fibers are oriented in chaotic directions and are surrounded by numerous cardiac fibroblasts and extracellular matrix.

Question 21

Healthy, hypertension-induced hypertrophy, and hypertrophic cardiomyopathy.

Which is which?

Answer 21

A. Normal

B. HTN

C. HCM

Question 22

Pathophysiology of hypetrophic cardiomyopathy

Answer 22

Question 23

Why do so many hypertrophic cardiomyopathy patients have systolic outflow tract obstruction?

Answer 23

Question 24

Why are beta blockers and other negative inotropes helpful for patients with HCM?

Answer 24

1. Reduced myocardial oxygen demand
2. Reduced mitral regurgitation and outflow obstruction via the mitral leaflet obstructive mechanism

For the same reason, beta 1 agonists are contraindicated in all these patients

Question 25

HCM usually presents around age ___

Answer 25

HCM usually presents around age ~25

Question 26

In HCM patients with mitral leaflet outflow tract obstruction, ___ may be induced by exertion.

Answer 26

In HCM patients with mitral leaflet outflow tract obstruction, syncopy may be induced by exertion.

Orthostasis sometimes causes syncopy in these patients for the same reason - transient rise in endogenous positive inotropes (epinephrine, norepinephrine)

Question 27

In both dilated cardiomyopathy and hypertrophic cardiomyopathy, a complicating ___ may be fatal.

Answer 27

In both dilated cardiomyopathy and hypertrophic cardiomyopathy, a complicating atrial fibrillation may be fatal.

Question 28

The greatest concern in untreated hypertrophic cardiomyopathy patients is ___, resulting in ___.

Answer 28

The greatest concern in untreated hypertrophic cardiomyopathy patients is ventricular fibrillation, resulting in sudden death.

This particularly happens in young adults during strenuous physical exercise. Risk factors among HCM patients include: history of syncopy, family history of sudden death, high-risk category mutations, and extreme LV wall hypertrophy

Question 29

Common physical exam findings of hypertrophic cardiomyopathy

Answer 29

• S4
• “Double apical impulse” : Forceful atrial contraction may also result in a palpable presystolic impulse over the cardiac apex

Question 30

Valsalva maneuver

Answer 30

Asking the patient to “bear down” (technically defined as forceful exhalation with the nose, mouth, and glottis closed).

Increases intrathoracic pressure, which decreases venous return to the heart and transiently reduces LV size.

During Valsalva, the murmur of HCM increases in intensity. In contrast, the murmur of aortic stenosis decreases in intensity during Valsalva because of the reduced flow across the stenotic valve.

Question 31

Sudden change from standing to a squatting position

Answer 31

Augments venous return to the heart (which increases preload) while simultaneously increasing the systemic vascular resistance.

Causes the murmur of aortic stenosis to become louder. In contrast, the transient increase in LV size during squatting softens the intensity of the HCM murmur.

Question 32

Diagnostic studies for HCM

Answer 32

• ECG
• Echo
• Cardiac cath
• Genetic testing

Question 33

Treating hypertrophic cardiomyopathy

Answer 33

• Beta blockeres
• Calcium channel blockers
• Diuretics for those who develop pulmonary edema, but requires careful dosing to avoid depletion
• Antiarrhythmics (amiodarone and disopyramide)
• Avoidance of strenuous exercise
• Surgery for refractory cases (myomectomy or percutaneous septal ablation)
• Genetic counseling
• Contraindicated drugs: beta 1 agonists, vasodilators (including nitrates)

Question 34

Both dilated and hypertrophic cardiomyopathies may be caused by ___.

Answer 34

Both dilated and hypertrophic cardiomyopathies may be caused by dysfunctional β-Myosin heavy chain formation

Question 35

Common phenomena which cause decompensation in chronic left ventricular systolic heart failure.

Answer 35

• Acute intravascular volume increase
• Fever
• Myocardial ischemia
• Abrupt discontinuation of antihypertensives

Question 36

Ejection in hypertrophic cardiomyopathy

Answer 36

Despite that muscle fibers have somewhat scattered force vectors, in hypertrophic cardiomyopathy, contractility is typically normal or even hyperdynamic, but relaxation is abnormal due to decreased compliance of the LV.