An Overview of Cardiomyopathy

Some important characteristics of Diastolic Dysfunction (DD) heart failure are:

1. Impaired heart relaxation.  (This is another clinical name for DD.)
2. Normal ejection fraction (EF).  (This is also another name for DD.)
3. Decreased cardiac output (CO).  (CO = amount of blood pumped out per minute.)
4. Increased end diastolic pressures at lower volumes.

Diastolic Dysfunction is usually used to describe Hypertrophic and Restrictive Cardiomyopathic patients:

Hypertrophic Cardiomyopathy (HCM) – Left and/or right ventricular hypertrophy, often asymmetrical, which usually involves the interventricular septum.  Mutations in the sarcoplasmic proteins cause the disease in many patients.  (See picture on the BOTTOM LEFT.) 

Restrictive Cardiomyopathy (RCM) – Restricted filling and reduced diastolic size of either or both ventricles with normal or near-normal systolic function.  Idiopathic or associated with other disease (e.g. amyloidosis, endomyocardial disease.)  (See picture on the BOTTOM RIGHT.)

Though they both have different etiologies, their general hemodynamic and pathophysiological presentations are similar, involving impairment in relaxation aka diastolic dysfunction.

We were shown an echo of a heart with thickened ventricles.  The lateral walls and interventricular septum are both thickened (hypertrophied).  There is good contractility but the end diastolic volume (EDV) is limited.  As a consequence, there is a decreased CO despite a normal EF (~80%).  The CO is impaired because the amount of blood being pumped out in each heart beat is severely limited by the inability of the ventricle to relax.  This is a consequence of both restrictive and hypertrophic cardiomyopathies.

Restrictive Cardiomyopathies

Characteristics:

1. Hallmark = abnormal diastolic function.  (Duh!)
2. Ventricular walls are excessively rigid and impede ventricular filling
3. Systolic function often remains normal and preserved.

The difference between RCM and HCM is that RCM has multiple etiologies for its clinical presentation.  It is most commonly related to infiltrative diseases, the most important ones being Amyloidosis and Sarcoidosis.  There are other etiologies on the slide, but they weren’t stressed.  He just mentioned that there are many systemic diseases that cause myocardial impairment, resulting in restrictive cardiomyopathies.
 

Restrictive Amyloid

• Primary Amyloid – The problem is an immunoglobulin light chain from a monoclonal population of plasma cells.   Primary amyloid involves the heart and is the most common cause of death.  Multiple myeloma is a disease that often leads to it.
• Secondary, familial, and senile amyloid are listed on the slide but weren’t mentioned in class.

Restrictive Sarcoid

• A granulomatous disorder of unknown cause.  It causes diffuse pulmonary fibrosis that leads to fatal right-sided heart failure.  Primary cardiac involvement is not often recognized clinically – in autopsy it’s seen 20-30% of the time.

Clinical Manifestations & Physical Findings (similar to Systolic Dysfunction):

1. Exercise intolerance and weakness.
2. Elevated central venous pressure with attendant edema, ascities, and enlarged tender liver.
3. Jugular venous distension (JVD).
4. Heart sounds are distant with S3 and S4 sounds commonly heard.

Diagnostic Studies:

1. ECG – Low voltage is particularly seen in Amyloid due to infiltrations of the heart that cause decreased electrical current flowing through the cells.
2. Echo – Incredibly important for looking at myocardial function.  It helps to determine if there is systolic or diastolic impairment of the heart, if the walls are thick or thin, etc.

Hypertrophic Cardiomyopathies

Characteristics:

1. Left ventricular hypertrophy of a nondilated left ventricle (LV) without obvious antecedent cause (i.e. not secondary to a cardiovascular or systemic disease such as hypertension or aortic stenosis).
2. Physiologically characterized by diastolic dysfunction – abnormal stiffness of the LV with resultant impaired ventricular filling leading to pulmonary congestion and dsypnea.
3. Other names: Idiopathic Hypertrophic Subaortic Stenosis (IHSS) or Hypertrophic Obstructive Cardiomyopathy (HOCM).
4. Only 25% of patients with a hypertrophic cardiomyopathy have an outflow gradient in the left ventricle.  This used to be one way of defining the disease, but isn’t any longer due to the small percentage of patients who have it.

HCM is often seen in young athletes who die suddenly.  Dr. Klapholz showed us an echo of HCM – the walls are very thickened with the suggestion of mid-cavitary obliteration.  The walls are so thick that during systole, they obliterate the ventricular cavity; this is not seen in normal hearts.  As a consequence, portions of the ventricle are trapped and unable to eject blood because the walls touch each other during systole.  If they touch in the midportion of the ventricle, the apex is unable to be emptied.

Genetics:

• 50% of HCM is familially linked as an autosomal dominant trait with loci on several chromosomes and greater than three dozen different mutations.
• Echo studies have shown that even in first degree relatives who haven’t manifested the hypertrophy yet, 25% of them have evidence of the disease by genetic analysis.
• The phenotype usually appears in adolescence and early adulthood.  The consequences, most often being death, occur when the patient is in his 20s or 30s.

Pathophysiology:

• HCM obstruction is dynamic as apposed to fixed obstruction as seen in aortic stenosis.  If you can somehow keep the ventricles distended, you can eliminate the mid-cavitary obliteration.
• Diastolic dysfunction is a consequence of the hypertrophy which leads to slowed relaxation.  Because the muscle is so thick, it outweighs the blood supply – so despite the absence of coronary artery disease, the thickness of the muscle outstretches the ability of the capillaries to supply oxygen so the muscle can contract normally.  This leads to even further impairment of relaxation of the muscle.

High vs. Low Risk Outcome:

• High risk:
  • Previous cardiac arrests/sustained ventricular tachycardia
  • Familial history of sudden death
  • Adverse genotype
  • Recurrent syncope
• Clinically, we make an effort to distinguish high vs. low risk HCM by routinely doing genetic screening (esp. in high-school and professional athletes).

Clinical Manifestations:

1. Sudden death often during or after physical exercise.  (Most important!!)
2. Most common complaints are dyspnea, angina, and syncope.
   1. These athletes who are playing competitive sports have to compensate for the decreased CO that’s secondary to their small diastolic volume.  If they’re not able to do that à fainting or death. 

 Lab evaluation done with echo and genetic typing helps determine prognosis.  It is recommended that patients with high risk not participate in competitive sports.

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