Cardiovascular Anatomy and Physiology Flashcards

The inferior wall of the left ventricle is primarily supplied by which coronary artery?

Answer: Right Coronary Artery (RCA)

In a right-dominant circulation (most common), the posterior descending artery (PDA) supplies the inferior wall. The PDA is a branch of the right coronary artery (RCA). Therefore, an occlusion of the RCA is the most common cause of an inferior wall myocardial infarction.

What is the intrinsic firing rate of the atrioventricular (AV) node when it acts as the primary pacemaker?

Answer: 40-60 beats per minute

The cardiac conduction system has a hierarchy of pacemakers. The SA node is the primary pacemaker (60-100 bpm). If it fails, the AV node takes over at its intrinsic rate of 40-60 bpm, resulting in a junctional escape rhythm.

In a patient with severe aortic stenosis, what pressure gradient finding is expected during a left heart catheterization?

Answer: Peak systolic LV pressure is significantly higher than peak systolic Ao pressure

Aortic stenosis is a narrowing of the aortic valve, which obstructs blood flow from the left ventricle (LV) to the aorta (Ao). To overcome this obstruction, the LV must generate a much higher pressure during systole compared to the pressure in the aorta. This difference is the peak-to-peak or mean pressure gradient across the valve.

The Frank-Starling mechanism of the heart describes the relationship between:

Answer: Preload and stroke volume

The Frank-Starling law states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the ventricles (the end-diastolic volume). The increased volume stretches the ventricular wall, causing cardiac muscle to contract more forcefully. This relationship is between preload (ventricular stretch/volume) and contractility (stroke volume).

During a right heart catheterization for an atrial septal defect (ASD), the most significant oxygen saturation 'step-up' would be found between which two chambers?

Answer: Superior Vena Cava and Right Atrium

An ASD allows oxygenated blood from the left atrium to shunt into the right atrium, mixing with deoxygenated systemic venous return. This causes the oxygen saturation of blood in the right atrium to be significantly higher than the blood in the superior and inferior vena cava. This 'step-up' in saturation is the hallmark diagnostic finding for an ASD.

Which component of the cardiac cycle is represented by the T-wave on an electrocardiogram (ECG)?

Answer: Ventricular repolarization

The ECG records the electrical activity of the heart. The P-wave represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T-wave represents the repolarization of the ventricles. Atrial repolarization is typically obscured by the much larger QRS complex.