14. HCM

Question 1

List the common and training-related abnormalities of an athlete’s ECG.

Answer 1

• Sinus bradycardia
• 1° AV block
• Incomplete RBBB
• Early repolarization
• Isolated QRS voltage criteria for LV hypertrophy

Question 2

List the uncommon and training-unrelated abnormalities of an athlete’s ECG.

Answer 2

• T wave inversion
• ST segment depression
• Pathological Q waves
• LA enlargement
• L or R axis deviation
• RV hypertrophy
• Ventricular pre-excitation
• Complete LBBB or RBBB
• Long or short QT interval

Question 3

What is a genetic CV disease? Characteristics?

Answer 3

Diseases in which one’s inherited genome is the prime determinant of the presence of serious CV disease

• Often fatal at an early age
• Majority are asymptomatic as they develop

Question 4

What is homocysteinuria? How does it develop?

Answer 4

• Inherited metabolic disorder w/ SNPs disabling enzymes involved in interconversion/breakdown of sulphur-AAs, methione and cysteine
• Homocysteine builds up in the bloodstream, damaging the arterial endothelial lining –> accelerated atherosclerosis and clotting events

Question 5

Risks for individuals homozygous for homocysteinuria? Heterozygotes?

Answer 5

• Homo = begin having heart attacks and strokes in their teens and twenties
• Hetero = at increased risk for MI in mid-life (40-60 years old)

Question 6

What % of sudden cardiac deaths in young athletes does genetic CV disease account for?

Answer 6

40%

Question 7

What is the most common cause of sudden cardiac death in young athletes during exercise?

Answer 7

Hypertrophic cardiomyopathy

Question 8

What is hypertrophic cardiomyopathy?

Answer 8

Hypertrophy that occurs in the absence of other obvious circulatory or valvular deficiencies such as hypertension and aortic stenosis

Question 9

In what pattern is hypertrophic cardiomyopathy inherited?

Answer 9

Inherited in an autosomal dominant pattern

Question 10

What fraction of the US population has hypertrophic cardiomyopathy?

Answer 10

1/500 peeps

Question 11

What happens to the integrity of cardiac tissue as a consequence of HCM? Significance?

Answer 11

• Increased fibrosis (interweaving of muscle and connective tissue)
• Make cardiac muscle stiff, low compliance, low stretch –> impairs diastolic filling

Question 12

How does hypertrophy cause an energy imbalance? What can this ultimately lead to?

Answer 12

• Relative decrease in number of capillaries and increase in distance b/t capillaries
• Increased ratio of myofibrils to mitochondria
• Leads to ischemia b/c energy cost goes up, but O₂ not increasing proportionally

Question 13

What characterizes diastolic dysfunction? Symptoms?

Answer 13

• Impaired filling due to abnormal relaxation and increased chamber stiffness
• Increased LA and LV end diastolic pressure
• Sx: pulmonary congestion, exertional dyspnea, syncope

Question 14

What is asymmetric septal hypertrophy?

Answer 14

Septum is growing into groove that should be LV outflow into aorta –> blood gets backed up

Question 15

What is the pathology of hypertropic cardiomyopathy?

Answer 15

• Cardiac myocytes are outgrowing blood supply
• Energy cost is sky-rocketing due to both muscle mass & outflow obstruction
• Stiff, fibrotic muscle impairs cardiac filling

Question 16

What is the most common first symptom of hypertrophic cardiomyopathy?

Answer 16

Sudden death

Question 17

Describe the cycle of pathologic hypertrophy of HCM.

Answer 17