Cardiomyopathies (Almendral) - 11/14/16

Question 1

What is a cardiomyopathy?

Answer 1

• Disease of the heart muscle itself - hence PRIMARY cardiomyopathy
  
  • Structurally and functionally abnormal
• Frequently genetic
• Isolated cardiac disorder or part of systemic disease
• Not due to CAD, HTN, or valve disease

Question 2

Cardiomyopathies (5)

Answer 2

Based on appearance and physiology

1. Dilated cardiomyopathy
2. Hypertrophic cardiomyopathy
3. Restrictive/infiltrative cardiomyopathy
4. ARVC (arrhythmogenic RV) cardiomyopathy
5. Unclassified

Question 3

Dilated cardiomyopathy

Definition

Answer 3

most common - up to 90%

Enlarged ventricles (eccentric hypertrophy - sarcomeres added in series) + systolic dysfunction

Question 4

Hypertrophic cardiomyopathy

Definition

Answer 4

Ventricular hypertrophy + diastolic dysfunction

Question 5

Restrictive cardiomyopathy

Definition

Answer 5

Abnormally stiffened myocardium (b/c of fibrosis or infiltrative process) + diastolic dysfunction

Question 6

Dilated Cardiomyopathy:

Causes

Answer 6

• Idiopathic
• Familial (genetic)
  
  • Up to 50% idiopathic CM likely familial
• ABCCCD
  
  • Alcohol abuse
    
    • Reversible if early
  • wet Beriberi
  • Coxsackievirus group B
  • chronic Cocaine use
  • Chagas disease
  • Doxorubicin toxicity

Question 7

Dilated Cardiomyopathy:

Pathophysiology

Answer 7

• ventricular dilatation w/ decreased contractile function
• Impaired myocyte contractility → ventricular SV and CO decline → two compensatory effects activated:

1. Frank-Starling mechanism - elevated ventricular diastolic volume increases stretch of myofibers –> inc. subsequent stroke volume
2. Neurohormonal activation initially mediated by SNS –> inc. HR and contractility will help to buffer fall in CO

Ultimately, however, the “compensatory” effects of neurohormonal activation prove detrimental:

• Arteriolar vasoconstriction + increased systemic resistance make it more difficult for LV to eject blood in forward direction
• Rise in intravascular volume further burdens ventricles
• Result: pulmonary and systemic congestion

Question 8

Dilated cardiomyopathy:

Physical exam

Answer 8

• HF
• S3 (poor systolic function)
• Systolic regurgitant murmur (result of significant LV dilatation)
• Dilated heart on EKG
  
  • (LVH on EKG is non-specific… dilated CM does not mean hypertropy)
• Balloon appearance of heart on CXR

Question 9

Dilated cardiomyopathy:

Treatment

Answer 9

• Na+ restriction
• ACE inhibitors
• Beta-blockers
• Diuretics
• Digoxin
• ICD (implantable cardioverter-defibrillator)
• Heart transplant

Most recover, usually 1/3 progress to HF

Question 10

Hypertrophic cardiomyopathy:

60-70% of cases are familial, autosomal dominant; associated with what type of mutation?

Answer 10

Beta-myosin heavy-chain mutation

• Mutation in several sarcomeric genes

Also causes:

• Myocyte disarray

Question 11

Hypertrophic cardiomyopathy:

Characteristics

Answer 11

• Asymmetric LVH
  
  • Reduces compliance and diastolic relaxation properties of the chamber –> filling becomes impaired
• LVOT - aorta can’t get blood
• Can be associated with Friedreich ataxia
• Causes syncope (drop in BP) during exercise
• May lead to sudden death in young athletes
  
  • Prone to ventricular arrhythmia (due to fibrosis)

Question 12

Hypertrophic cardiomyopathy: pathophysiology

Answer 12

Question 13

Hypertrophic cardiomyopathy:

Findings

Answer 13

• S4 (atrial contraction into stiff LV)
• Systolic murmur
• May see mitral regurg due to impaired mitral valve closure

Question 14

Hypertrophic cardiomyopathy:

Treatment

Answer 14

• Cessation of high-intensity athletics
• Beta-blocker
  
  • ​Reduce contractility (negative inotrope)
  • Reduce HR (negative chronotrope) - want LV cavity to be as filled as possible to minimize obstruction
• Non-dihydropyridine Ca2+ channel blockers (e.g. verapamil)
• Disopyramide (Class 1A Anti-arrhythmic)
  
  • Reduce contractility → Reduce obstruction → Reduce O2 demand
  • Reduce HR → inc. diastolic filling time
• ICD if patient is high risk

AVOID DIURETICS, VASODILATORS

• Dihydropyridine CCBs
• ACEI/ARBs
• NTG

Question 15

Restrictive cardiomyopathy: characteristics

Answer 15

• Rare
• Abnormally rigid (but not necessarily thickened) ventricles
• Problem with relaxation (so size on CXR looks the same)
• Diastolic dysfunction
  
  • Impaired diastolic filling but usually near normal systolic function
    
    • Result from either fibrosis or scarring of endomyocardium
    • Infiltration of myocardium by abnormal substance
• Near normal LVEF except in late stages

Question 16

Restrictive cardiomyopathy:

Causes

Answer 16

• Sarcoidosis
• Amyloidosis
• Postradiation fibrosis
• Endocardial fibroelastosis
  
  • Thick fibroelastic tissue in endocardium of young children
• Loffler syndrome
  
  • Endomyocardial fibrosis w prominent eosinophilic infiltate
• Hemochromatosis
  
  • Although dilated cardiomyopathy is more common

Question 17

Restrictive cardiomyopathy:

Pathophysiology

Answer 17

• Dec compliance → Inc filling pressures → inc systemic and pulmonary venous pressures → volume overload
• Dec. cavity size → Dec. SV → Dec. CO

Question 18

Arrhythmogenic RV Cardiomyopathy (ARVC)

Answer 18

• Genetic disorder
• RV free wall replaced by fibro-fatty tissue
  
  • So fat found in RV
• RV dysfunction, dilatation

Question 19

Unclassified CM: Stress-induced CM

Answer 19

LV Non-compaction

• Genetic disorder

Takotsubo CM (broken heart syndrome)

• Mid-LV ballooning
• Precipitated by emotional or physical stress