The

complex (wave) represents the sum of all ventricular muscle cell depolarizations

Coronary artery disease (CAD) is a condition where the arteries that supply blood to the heart become narrowed or blocked due to a buildup of plaque. Several risk factors contribute to the development of CAD, including diabetes mellitus, hypertension, obesity, high alcohol consumption, smoking, and a family history of CAD.

Research suggests that individuals with diabetes mellitus are two to four times more likely to develop CAD than those without diabetes. This is because diabetes can lead to damage to the blood vessels and nerves that control the heart, as well as increased inflammation and high levels of blood glucose that can contribute to the buildup of plaque in the arteries.

While hypertension, obesity, and high alcohol consumption are also known risk factors for CAD, they generally do not increase the risk to the same degree as diabetes. Nonetheless, these factors can contribute to the development and progression of CAD and should be addressed through lifestyle modifications and medical interventions.

In the normal electrocardiogram, the PR interval represents

The PR interval represents the time from the onset of atrial activation to the onset of ventricular activity. During this time, the electrical impulse travels through the atria, the atrioventricular (AV) node, and the bundle of His before entering the ventricles and initiating ventricular depolarization. Option A is incorrect because the atrial depolarization is represented by the P wave. Option B is incorrect because the ventricular depolarization is represented by the QRS complex. Option D is incorrect because there is no such term as “electrical systole” of the ventricles in ECG interpretation.