Tuesday, March 27, 2012

Cardiomyopathies – Heart diseases | Types of Cardiomyopathies

Cardiomyopathies are the heart diseases resulting from a primary abnormality in the myocardium. Features of inflammation are minimal. Cardiomyopathy should be suspected in a young normotensive patient who develops heart failure in the absence of congenital, valvular or ischemic heart disease.

Types of Cardiomyopathies

Dilated (congestive) cardiomyopathy: It is characterized by progressive cardiac hypertophy, dilation and contractile (systolic) dysfunction resulting in failure of ventricle to empty in systole. Most cases develop heart failure. Cause is not detectable in most of the cases. A few cases are associated with:
  • Viral infections e.g conxsakievirus B.
  • Metabolie diseases e.g hypothyroidism hyperthyroidism and thiamine deficiency.
  • Alcoholism.

Hypertrophic Cardiomyopathy
It also referred to as asymmetrical septal hypertrophy and idiopathic hypertrophic subaortic stenosis. This condition is characterized by marked hypertrophy of the ventricular muscles with resistance to diastolic filling. Selective hypertrophy of the septum immediately below the aortic valve, obstructing the left ventricular outflow tract. Both ventricles are diffusely involved in most cases. In about 50% cases the disorder is inherited as an autosomal dominant trait. The interventricular septum is substantially thicker than the free lateral wall of the left ventricle.

Asymmetric hypertrophy is often associated with a significant degree of ventricular outflow obstruction during systole. In this group of patients, the systolic obstruction is caused by abnormal anterior motion of mitral valve leaflet during systole.

Clinical Features: The basic abnormality in hypertrophic cardiomyopathy is an inability to fill a hypertrophic left ventricle. Ejection is forceful but ineffective because the amount of blood in the left ventricle is very small. In addition there is obstruction of the left ventricle outflow. The limitation of cardiac output and a secondary increase in pulmonary venous pressure cause exertional dyspnea. Myocardial ischemia is common and anginal pain is frequent.

Restrictive Cardiomyopathy
It is characterized by a primary disease in ventricular compliance due to fibrosis and stiffness of ventricular walls, resulting in impaired ventricular filling during diastole. Exact cause unknown: myloidosis hemochromatosis and sarcoidosis are involved in some cases.

Clinical Features: The physiologic problem in restrictive cardiomyopathy is a stiff and inelastic ventricle that can be filled only with great effort. Clinically it presents with heart filure and angina.

Monday, March 26, 2012

What is Atrial Septal Defect (ASD)?

Atrial Septal Defect is the most common shunt lesion in adults. It often remains undetected until adulthood because patients are often asymptomatic. The condition remains unnoticed in infancy and childhood till pulmonary hypertension is induced causing late cyanotic heart disease and right-sided heart failure. A large ASD may be associated with growth failure in infants and children. It is more common in women thin in men.

There are three types of Atrial Septal Defect

Ostium Secundum ASD (75%)
It is the most common type (70% of patients) and results from defect in the region of the fossa ovalis. In this type there is no involvement of AV valves.

Ostium Primum ASD (15%)
It results from absence of septum primum at the lower portion of the atrial septum. It is more common in Down’s syndrome. It is more common in Down’s syndrome. In this type there is also involvement of AV valves.

Sinus Venosus Defect (10%)
It is in the upper part of the septum near the entrance of the inferior vena cava and coronary sinus therefore producing communication between coronary sinus and left atrium.

Blood flows from high pressured left atrium to low pressured right atrium (left to right shunt) through ASD. Pulmonary flow is increased and right ventricle is dilated and hypertrophied owing to the volume overload. With time, pulmonary vascular resistance increases resulting in pulmonary hypertension. This pulmonary hypertension in turn causes right heart failure or reversal of the left to right shunt (i.e now blood flows from right atrium to left atrium through this Atrial Septal Defect). Direct mixing of this deoxygenated blood produces cyanosis.
Above the age of 30 years there may be an increase in pulmonary vascular resistance, which gives rise to pulmonary hypertension. Atrial fibrillation is common at this stage.

Clinical Features
  • Asymptomatic for may years if there is small or moderate defect and no pulmonary hypertension. Normal or minimally diminished exercise tolerance may develop.
  • Exertional dyspnea after age 30
  • Palpitations due to atrial arrhythmia
  • Patients are more prone to develop recurrent pulmonary infections.
  • Right ventricular failure with large defect and prolonged pulmonary hypertension may develop later in life.

On CVS Examination
Systolic ejection murmur over the pulmonary area that does not vary with respiration.

X-ray Chest
  • Prominent pulmonary artery
  • Pulmonary plethora (plethora means fullness)
  • Right ventricular hyperthrophy

ECG: Shows incomplete right bundle branch block (RBBB) and right axis deviation.

Echocardiography: It can identify the type of defect, estimates pulmonary artery pressure, demonstrate right ventricular hypertrophy and pulmonary arterial dilation. It also demonstrates paradoxical motion of the interventricular septum. Doppler echocardiography is also required. Transesohageal echocardiography can detect small atrial septal defect that is missed on routine transchoracic 2-D echocardiography.

Cardiac Catheterization
It is performed unless the patient has large defect on echocardiography.
  • It is the definitive diagnostic procedure
  • It quantifies the shunt 
  • It measures pulmonary vascular resistance.

Aortic Stenosis | Symptoms, Treatment and Investigations

Obstructed left ventricular outflow due to aortic stenosis leads to increased left ventricular pressure and compensatory left ventricular hypertrophy. To maintain cardiac output large pressure gradient across the valve is required. Cardiac output at rest is maintained within normal limits in most patients with severe aortic stenosis, it often fails to rise normally during exertion. Late in the course of the disease, the cardiac ouput and stroke volume decline (due to LV dysfunction). Decreased flow of blood through the aortic valve causes decreased cardiac output, hypotension and syncope (fainting), myocardial ischemia and angina.

Ischemia in aortic stenosis : Due to hypertrophy, heart requires more blood for oxygenation that may be not be possible in severe aortic stenosis resulting in myocardial ischemia even in the absence of coronary artery disease. High left ventricular pressure may compress the coronary arteries in systole and shorten the diastole phase may lead to reduced coronary blood flow manifesting as myocardial ischemia, angina, arrhythmias and left ventricular failure. This ischemia becomes more severe on exercise.

  • Rheumatic heart disease
  • Congenital bicuspid aortic valves
  • Calcification of valves in old age

Clinical Features

  • Long asymptomatic phase
  • Symptomatic aortic stenosis manifests as angina, exercise induced syncope, exertional dyspnea and ultimately heart failure and sudden death. These symptoms appear when the aortic orifice in reduced to one-third of its normal size.
  • On auscultation there is an ejection systolic murmur at aortic area.


Xray Chest
  • Chest X-ray may be normal in critical aortic stenosis
  • The heart is usually normal in size or slightly enlarged
  • Post-stenotic dilatation of ascending aorta on PA view is commonly seen.

  • Left ventricular hypertrophy.
  • Left ventricular strain due to pressure overload. Left atrial enlargement.

  • This shows thickened, calcified and immobile aortic valve cusp.
  • Detects left ventricular hypertrophy, its systolic and diastolic function.
  • Droppler echocardiography demonstrates the pressure gradient across the valve and the valve area.


Medical treatment is not effective for aortic stenosis, any patient who develop any of the three symptoms (angina, syncope or heart failure) is the candidate for valve replacement.
Surgery is not indicated for asymptomatic patients except those with declining left ventricular function, very severe left ventricular hypertrophy and very high gradient (>80 mmHg) or severely reduced valve area (<0.7 cm2).

Mitral Regurgitation (MR)

Mitral Regurgitation

  • Rheumatic heart disease (most common cause).
  • Mitral valve prolapse.
  • Chronic left ventricular failure with dilatation of the mitral valve ring may cause functional mitral regurgitation.
  • Connective tissue disorders e.g. SLE, rheumatoid arthritis.
  • Hypertrophic cardiomyopathy.
  • Collagen abnormalities such as Marfan’s syndrome, Ehlers-Danlos syndrome.
  • Acute MR may occur due to rupture of chordae tendineae a complication of infective endocarditis or rupture of papillary muscles due to myocardial infarction.

  • Regurgitation of blood from left ventricle to the atrium occurs throughout systole. During diastole, regurgitant blood flows back across the mitral valve. Left ventricular volume is greatly increased, being the sum of cardiac output plus the regurgitant flow; the left ventricle is thus dilated and hypertrophied.
  • The left atrium, which accepts both the pulmonary venous return and regurgitent flow is also dilated in chronic cases. Left arterial pressure and pulmonary venous pressure are increased. In chronic ases, there is pulmonary fibrosis, pulmonary arterial hypertension and right ventricular hypertrophy followed by failure. Acute mitral valve regurgitation produces pulmonary edema and acute left heart failure.

Clinical Features
  • Features of left heart failure such as exertional dyspnea.
  • Palpitation due to atrial fibrillation.
  • On auscultation there is soft first heart sound, a loud third heart sound and pansystolic murmur at apex.


X-ray Chest: This shows cardiomegaly due to left atrial and left ventricular enlargement. Pulmonary hypertension may be evident, pulmonary edema and pleural effusion in case of heart failure.

  • Bifid P wave due to left atrial hypertrophy
  • Left ventricular hypertrophy occurring in about 50% of cases and manifests as:
  • Right ventricular enlargement in some patients.

This shows dilated left atrium and left ventricle. It confirms the diagnosis of mitral regurgitation. Severity of Mitral Regurgitation can also be assessed.

Medial treatment in mild to moderate cases. Mitral valve repair or replacement in severe cases.

Causes, Pathogenesis, Morphology of Acute Myocardial Ischemia and Myocardial Infarction (MI)

  1. Thrombosis superimposed on a complicated stenosing atheroma is the basic cause of acute myocardial ischemia and myocardial infarction.
  2. The risk factors of atherosclerosis are hypercholesterolemia, cigarette smoking, diabetes mellitus, physical inactivity and use of oral contraceptives. Checkout risk factors.
  3.  Myocardial necrosis begins within approximately 20-30 minutes after coronary artery occlusion.
  4. Subendocardial region of myocardium is the most poorly perfused region of the ventricular wall and therefore myocardial infarct typically begins in the subendocardial region. The infarct usually reaches it full size within a period of 3-6 hours (During this period of infarction in evolution lysis of thrombus by administration of thrombolytic agents e.g. streptokinase or tissue plasminogen activator may limit the size of the infarct.
  5. Location of infarct depends on the coronary artery involved e.g.
    1. Occlusion of anterior descening artery (LAD) leads to infarction in anterior and apical areas of left ventricle and adjacent anterior 2/3 of interventricular septum.
    2. Occlusion of right coronary artery (RCA) leads to infarction in posterior wall of left ventricle, posterior 1/3 of interventricular septum.
    3. Occlusion of left circumflex artery (LCx) leads to infarction in lateral wall of left ventricle.
  6. Size of infarct depends on the following factors:
    1. Which segment of artery is blocked: Occlusion of proximal segments of the coronary arteries produces larger infarcts, involving the full thickness of the myocardium. Conversely, occlusion in more distal arterial branches tend to cause smaller infarcts.
    2. Degree of collateral circulation: In patients with long-standing coronary atherosclerosis, collateral circulation may develop over time in response to chronic ischemia. Such collateral vessels may limit the size of the infarct.

Consequences of Acute Myocardial Ischemia
The Acute myocardial ischemia has four possible consequences:
1.      It may only induce an attack of angina.
2.      More severe ischemia may result in myocardial infarction limited to inner 1/2  some portion or the entire circumference of the left ventricular wall to produce subendocardial foci of ischemic necrosis, also called subendocardial infarct.
3.      The ischemic necrosis (infarction) may traverse the entire thickness of some portion of the left ventricular wall, creating transmural infarct.
4.      Sudden cardiac death.

1.      Transmural infarct: Greater than 2.5 cm and traverses from endocardium to subepicrdial myocardium. It is more common than subendocardial one.
2.      Subendocardial infarct: Multifocal area of necrosis confined to inner 1/3 – 1/2 of the left ventricular wall.
3.      Sequence of Morphologic Changes in Transmural Infarct

Morphologic changes in myocardial infarction depend on the time passed from onset. There is coagulation necrosis and inflammation followed by formation of granulation tissue, resorption of necrotic material and finally organization of the granulation tissue to form a fibrous scar.