Myopathic Flashcards
1
Q
Define Cradiomyopathy
A
Cardiomyopathy is a broad term used to describe a variety of issues that result from disease of the myocardium.
2
Q
Define Hypertrophic cardiomyopathy
A
Hypertrophic cardiomyopathy (HCM) is a genetic disorder characterised by left ventricular hypertrophy without an identifiable cause.
3
Q
What is cardiomyopathy?
A
- Cardiomyopathy is a group of diseases of the myocardium that affect mechanical or electrical function of the heart.
- It is one of the causes of heart failure.
4
Q
What is myopathy?
A
Myopathy is a general term referring to any disease that affects the muscles that control voluntary movement in the body.
5
Q
What are the types of cardiomyopathy?
A
- Dilated - this is the main cause of heart failure
- Hypertrophic - less common but still cause heart failure
- Restrictive - less common but still cause heart failure
6
Q
What is the aetiology of hypertrophic cardiomyopathy?
A
- Autosomal dominant mutation
- Autosomal dominant trait: genetic missense mutation in one of the genes that encode proteins in the sarcomere of heart muscle.
- Beta-myosin heavy chain mutation is the most common, but it could also be mutations in the myosin binding protein C and Troponin T.
- 50% of mutations are sporadic
- It is a primary form of cardiomyopathy i.e. not in response to other underlying disease e.g. hypertension or valvular disease
- Autosomal dominant trait: genetic missense mutation in one of the genes that encode proteins in the sarcomere of heart muscle.
7
Q
What is the pathophysiology of HT CM?
A
- Diastole is the main issue not systole.
- The heart is stiff and does not relax properly.
- The left ventricle becomes hypertrophied and hypertrophy is asymmetrical, blocking the left ventricle outflow tract during systoles.
8
Q
Skipped detailed pathophysiology of hypertrophic cardiomyopathy
A
9
Q
What is the epidemiology of hypertrophic Cardiomyopathy?
A
- It is the most common genetic heart disease.
- The most frequent cause of sudden cardiac death in young people.
- May present at any age
- Second most common cardiomyopathy (after dilated)
- 0.2% prevalence
10
Q
What are the symptoms of HT CM?
A
- Chest pain - Angina
- Dyspnoea - shortness of breath
- Palpitations
- Dizziness - Dizzy spells
- Syncope - fainting
- Sudden death, may be first manifestation
11
Q
What are the signs of HT CM?
A
-
Ejection systolic murmur: crescendo-decrescendo character due to blood flowing through the obstructed left ventricular outflow tract.
- The intensity of the murmur can change depending on the level of obstruction
- When squatting vascular resistance increases, which makes it harder to eject blood out and increases afterload. This means that the ventricle has more blood stretching it out, so it becomes less obstructed, and the murmur becomes less intense.
- When standing or doing a valsalva maneuver, venous return decreases. This decreases preload so less blood is stretching out the ventricle before ejection. The obstruction gets larger and the murmur’s intensity increases.
- The intensity of the murmur can change depending on the level of obstruction
- S4 sound
- S4 sound: due to atria contracting and pushing blood into a non-compliant ventricular wall during diastole.
- Bifid pulse: two pulses due to mitral valve moving towards outflow tract mid-systole and causing further obstruction
- Systolic thrill may be felt
- Arrhythmias
- Hypertrophy seen on imaging
12
Q
What investigations can be done for HT CM?
A
- Microscopically
- Myocyte disarray
- Ultrastructural level, myofibrils are in disarray
- When stained it turns blue
- Fibrosis is an electrical insulator – electrical current has to go around the fibrosis and causes arrhythmia
- Hypertrophy can occur in coronary arteries – causes ischaemia
- ECG
- Usually always abnormal
- Deep T wave inversion
- Shows signs of left ventricular hypertrophy with progressive T wave inversion and deep Q waves; may also be AF, WPW syndrome, ventricular ectopics, VT
- Echocardiogram: shows ventricular hypertrophy and a small left ventricular cavity; mid-systolic closure of aortic valve; anterior movement of mitral valve mid-systole
- Other
- MRI
- Exercise test
- Genetic analysis can confirm diagnosis since most cases are autosomal dominant and familial
13
Q
What is the management for HT CM?
A
- Antiarrhythmic medication - Amiodarone
- Calcium channel blocker - control heart rate.
- e.g. amlodipine, diltiazem
- Beta blocker - control heart rate.
- Atenolol
- Digoxin is contraindicated because it tends to increase force of contraction, which can increase the obstruction.
- Digoxin
- Contraindicated for acute myocardial infarction, ventricular fibrillation, hypersensitivity to the drug.
- Surgery
- Septal myectomy: surgery to remove part of septum causing obstruction
- Consider defibrillator if at high risk of arrhythmias
- Anticoagulation: if Atrial Fibrillation is present as there is higher risk of thrombus formation
14
Q
What are the complications of HT CM?
A
- Arrhythmias: as there is disarray of cardiac myocytes as well as due to the heart becoming ischaemic
- Atrial fibrillation
- Left ventricular outflow obstruction
- Blocked blood flow
- Heart failure
- Sudden cardiac death
- Sudden death: due to fast arrhythmias
- Mitral valve problems
- Dilated cardiomyopathy
15
Q
What are the risk factors for HT CM?
A
- Family history
- Friedreich’s Ataxia (autosomal recessive neurodegenerative disease): patients with Friedreich’s ataxia often develop hypertrophic cardiomyopathy
- Hypertension
- Obesity - Increases the risk of a clinical diagnosis
- Diabetes - Increases the risk of a clinical diagnosis
- Previous Myocardial infarction - Increases the risk of a clinical diagnosis
