Cardiovascular Pathophysiology and Heart Disorders

Valvular Heart Disorders (VHDs)

The heart relies on four primary valves—the atrioventricular valves (tricuspid and mitral) and the semilunar valves (pulmonary and aortic)—to ensure unidirectional blood flow. When these valves fail, it results in Valvular Heart Disorders (VHDs).

There are three primary mechanical failures in valves:

1. Stenosis: The valve opening becomes narrowed or stiff, restricting the forward flow of blood through the valve. Common examples include mitral stenosis and aortic stenosis.
2. Regurgitation: The valve fails to close completely, allowing blood to leak backward (retrograde flow). Examples include mitral regurgitation and aortic regurgitation.
3. Prolapse: The valve leaflets bulge backward into the atrium during contraction, often associated with regurgitation.

Rheumatic Heart Disease

A significant cause of valvular damage is Rheumatic Heart Disease. This is an autoimmune complication that follows an infection by Group A beta-hemolytic Streptococcus. In this condition, the body's immune response mistakenly attacks heart tissue due to molecular mimicry, where antibodies cross-react with the heart valves, eventually leading to valve sclerosis (hardening) and calcification.

Congestive Heart Failure (CHF)

Congestive Heart Failure is a progressive clinical syndrome where the heart is unable to pump sufficient blood to meet the metabolic demands of the body. It is categorized based on which side of the heart is failing and the specific nature of the dysfunction.

Left-Sided vs. Right-Sided Failure

• Left-Sided Heart Failure (LHF): When the left ventricle fails, blood "backs up" into the pulmonary circulation. This causes pulmonary congestion, leading to symptoms such as dyspnea (shortness of breath), orthopnea (difficulty breathing while lying flat), and the production of pink-tinged phlegm.
• Right-Sided Heart Failure (RHF): When the right ventricle fails, blood backs up into the systemic venous system. This results in peripheral edema (swelling in the legs and abdomen), hepatomegaly (enlarged liver), and distended neck veins (jugular venous distension).
• Biventricular Failure: Often, chronic left-sided failure eventually leads to right-sided failure, resulting in a combined state known as biventricular heart failure.

Systolic vs. Diastolic Dysfunction

Clinicians use the Ejection Fraction (EF) to differentiate between the two primary types of heart failure. The EF is the percentage of blood pumped out of the left ventricle with each contraction, calculated as:

$\text{EF} = \frac{\text{Stroke Volume}}{\text{End-Diastolic Volume}} \times 100\%$

• HFrEF (Systolic Heart Failure): Characterized by an $\text{EF} \leq 40\%$. In this state, the heart muscle has become too weak to squeeze effectively.
• HFpEF (Diastolic Heart Failure): Characterized by an $\text{EF} \geq 50\%$. Here, the heart muscle is often hypertrophied or stiff, meaning it cannot relax properly to allow the ventricles to fill with enough blood.

Exam Tip: If a patient presents with swelling in the legs and an enlarged liver, think Right-Sided failure. If they present with shortness of breath and pulmonary edema, think Left-Sided failure.