In ECG, a prolonged PR interval indicates
a) Myocardial ischemia and Hyperkalaemia
b) Cardiac arrhythmia and hypokalemia
c) Coronary artery disease and rheumatic fever
d) Hyperkalemia and hypokalemia

Hint: The ECG PR stretch compares to a delay of roughly 0.09 seconds. This postponement in the cardiovascular drive is critical as it shows that the Atria have launched out their blood into the ventricles first before the ventricles contract. This deferral is found in the piece of the heart that associates the atria and ventricles electrically.

Complete answer:
In ECG, the P-R stretch compares to the time delay in the A-V hub. The record or graphical portrayal of the electrical exercises of the heart which happen before the beginning of mechanical exercises is called an 'electrocardiogram' (ECG).
The time since the P wave begins (atrial depolarization) and the beginning of the QRS complex is the PR interval. This addresses the time needed to move through the atrium and through the AV-node into the ventricles for the electrical motivation produced in the sinus node. The normal PR range is between 0.12 and 0.20 seconds or 120 to 200 milliseconds (ms). The drawn-out PR range indicates that the nodal motivation of SA has been postponed and is called an AV block in the first degree. An extended PR span addresses a delay as soon as the sign crosses the atria at the heart, and the blood streams from the veins to the atria.

Hence, option C- Coronary artery disease and rheumatic fever is the correct answer.

Note:
Electrocardiography is a technique for examining the electrical activities of the heart. The 'electrocardiograph,' also known as the ECG machine, is a device that records the electrical activities of the heart. The operation of the SA hub pacemaker is measured in a roundabout way from the 'P' waves generated by atrial action. The QRS Complex in the ECG can be used to screen for ventricular withdrawal.