Cardiology Part-1 | Medicine Lectures

Cardiology is an important branch of medicine that studies the heart, its functions, blood flow, and heart-related disorders. For medical competitive exams, cardiology is a high-yield subject because many questions are asked from clinical signs, heart murmurs, diagnosis, and treatment basics. 

Among cardiology topics, valvular heart disease is particularly important, especially aortic and mitral stenosis. Other important topics include heart failure, constrictive pericarditis, cardiac tamponade, and pulmonary embolism. Aspirants should focus on concepts, symptoms, murmurs, and management to answer exam questions correctly.

Aortic Stenosis

Aortic stenosis is one of the most important valvular heart diseases for medical exams. The aortic valve is located between the left ventricle and the aorta. Its main function is to allow blood to flow from the left ventricle into the aorta and prevent backflow. The aortic valve usually has three cusps:

• Right coronary cusp

• Left coronary cusp

• Non-coronary cusp

The normal aortic valve opening is around 3 to 4 cm². Aortic stenosis occurs when this opening becomes narrowed, making it difficult for blood to leave the left ventricle.

Why Aortic Stenosis Is a Systolic Problem?

Aortic stenosis is called a systolic problem because the aortic valve opens during systole. During systole, the left ventricle contracts and pushes blood into the aorta. If the aortic valve is narrowed, blood cannot move out properly. This leads to:

• Reduced blood ejection

• Increased pressure on the left ventricle

• Increased workload on the heart

• Development of symptoms like fatigue, syncope, angina, and dyspnea

Causes of Aortic Stenosis

The causes of aortic stenosis differ by age group.

• Age-related degeneration: Common in elderly patients.

• Calcification of valve cusps: The valve becomes stiff and narrow.

• Congenital bicuspid aortic valve: Common cause in young individuals.

• NOTCH1 gene mutation: An important MCQ point related to bicuspid aortic valve.

• Atherosclerosis risk factors: Smoking, diabetes, dyslipidemia, and sedentary lifestyle can increase the risk.

In older patients, degenerative calcification is the most common cause. In younger patients, congenital bicuspid aortic valve is an important cause.

Pathophysiology of Aortic Stenosis

In aortic stenosis, the narrowed valve reduces the amount of blood ejected from the left ventricle. This causes a fall in stroke volume and reduced blood supply to different organs. Important effects include:

• Fatigue: Due to reduced blood supply to muscles.

• Syncope: Due to reduced blood flow to the brain.

• Angina: Due to increased oxygen demand of the thickened heart muscle.

• Dyspnea: Due to pressure backup into the lungs.

The left ventricle has to work harder to pump blood through the narrowed valve. This causes concentric left ventricular hypertrophy. Over time, this can lead to diastolic dysfunction and pulmonary congestion.

Clinical Features of Aortic Stenosis

The classic symptom triad of aortic stenosis is very important for exams. The triad includes:

• Angina

• Syncope

• Dyspnea

These symptoms occur because the heart is unable to pump enough blood effectively through the narrowed aortic valve.

• Low or normal blood pressure

• Weak pulse

• Slow-rising pulse in severe cases

• Usually undisplaced apex beat in pure aortic stenosis

Pulse Findings in Aortic Stenosis

Pulse findings are very important in aortic stenosis. Important pulse types include:

• Pulsus parvus: Low-volume pulse.

• Pulsus tardus: Slow-rising pulse.

• Pulsus parvus et tardus: Low-volume and slow-rising pulse, commonly seen in severe aortic stenosis.

This happens because blood leaves the left ventricle slowly and in reduced quantity due to the narrowed aortic valve.

Murmur in Aortic Stenosis

Aortic stenosis produces a systolic murmur because blood flows through the aortic valve during systole. The murmur is described as:

• Ejection systolic murmur

• Crescendo-decrescendo murmur

• Diamond-shaped murmur

• Heard after S1 and before S2

The murmur first increases in intensity and then decreases. This happens because blood flow velocity increases during rapid ejection and then decreases during slow ejection.

Management of Aortic Stenosis

The definitive treatment of aortic stenosis is aortic valve replacement.

• Aortic valve replacement is the final treatment.

• Medicines have a limited role.

• Diuretics may reduce preload and worsen symptoms.

• Beta-blockers may reduce contraction force and stroke volume.

• Drugs should be used carefully because they can worsen angina, syncope, or low output symptoms.

For exams, remember that there is generally no major role of pharmacotherapy in severe aortic stenosis.

Mitral Stenosis

Mitral stenosis is another important valvular heart disease. The mitral valve is located between the left atrium and the left ventricle. It allows blood to flow from the left atrium to the left ventricle during diastole and prevents backflow during systole. The mitral valve has:

• Anterior cusp

• Posterior cusp

• Papillary muscles

• Chordae tendineae

The normal mitral valve opening is around 4 to 6 cm². Mitral stenosis occurs when the valve opening becomes less than normal, causing obstruction to blood flow during diastole.

Causes of Mitral Stenosis

The most common cause of mitral stenosis is rheumatic heart disease. Rheumatic heart disease causes fibrosis and fusion of the mitral valve leaflets, leading to narrowing of the valve opening. Important causes include:

• Rheumatic heart disease

• Left atrial myxoma, rarely

• Fibrosis and fusion of valve leaflets

For competitive exams, rheumatic heart disease should be remembered as the most common cause of mitral stenosis.

Pathophysiology of Mitral Stenosis

In mitral stenosis, blood cannot flow easily from the left atrium to the left ventricle during diastole. This reduces left ventricular filling and decreases end-diastolic volume. As a result, stroke volume also decreases. This can cause:

• Fatigue

• Syncope

• Reduced systemic perfusion

• Pulmonary congestion

• Dyspnea

As the left atrium works harder to push blood through the narrowed valve, left atrial pressure rises. Over time, this leads to left atrial hypertrophy, left atrial dilation, pulmonary venous hypertension, pulmonary hypertension, and eventually right heart failure.

Murmur in Mitral Stenosis

Mitral stenosis produces a diastolic murmur because blood flows through the mitral valve during diastole. The classic murmur of mitral stenosis is:

• Mid-diastolic murmur

• Rumbling murmur

• Low-pitched murmur

• With pre-systolic accentuation

It is best heard:

• At the apex

• In the left lateral decubitus position

• During expiration

Pre-systolic accentuation happens because atrial contraction pushes blood forcefully through the narrowed mitral valve just before systole.

Management of Mitral Stenosis

The definitive treatment for mitral stenosis is balloon mitral valvotomy. This is useful because rheumatic mitral stenosis usually occurs due to fusion of valve leaflets. Important management points:

• Balloon mitral valvotomy is the definitive treatment.

• Valve replacement may be needed if balloon valvotomy is not possible.

• Rheumatic fever prophylaxis is important.

• Penicillin G may be used to prevent recurrent rheumatic fever and restenosis.

This treatment approach is different from aortic stenosis because mitral stenosis is commonly due to leaflet fusion, while aortic stenosis is often due to calcification.

Aortic Stenosis vs Mitral Stenosis

Aortic stenosis and mitral stenosis are important valvular heart diseases often asked in medical exams. Aortic stenosis is a systolic problem, while mitral stenosis is a diastolic problem. Check below the key differences in valve location, murmur type, symptoms, causes, and treatment.