A nurse is interpreting a client's ECG strip. Which of the following components of the ECG should the nurse examine to determine the time it takes for ventricular depolarization and repolarization?

D. Myocardial infarction (heart attack) is a common cause of cardiogenic shock. In myocardial infarction, part of the heart muscle becomes ischemic or necrotic due to occlusion of a coronary artery. This leads to impaired cardiac function and reduced cardiac output, resulting in cardiogenic shock. Prompt recognition and treatment of myocardial infarction are crucial to prevent or manage cardiogenic shock.
A. Anaphylaxis is a severe allergic reaction that can lead to systemic vasodilation and distributive shock, but it is not a common cause of cardiogenic shock. In anaphylaxis, the primary mechanism of shock is typically related to widespread vasodilation and increased vascular permeability rather than impaired cardiac function.
B. Hypovolemic shock occurs due to a decrease in intravascular volume, leading to inadequate tissue perfusion. It is not a common cause of cardiogenic shock, as the underlying mechanism is different. In hypovolemic shock, the primary issue is the loss of circulating blood volume, whereas cardiogenic shock involves impaired cardiac function.
C. Pulmonary embolism can lead to acute right heart strain or failure, which may result in hemodynamic instability and shock. However, pulmonary embolism typically causes obstructive shock rather than cardiogenic shock. Obstructive shock occurs when blood flow is obstructed, such as by a pulmonary embolism, leading to reduced cardiac output.

D. Atrial fibrillation can lead to irregular and often rapid heart rates, resulting in discrepancies between the apical (heart) and radial (peripheral) pulses. In atrial fibrillation, the atria fibrillate instead of contracting effectively, leading to irregular and sometimes asynchronous ventricular contractions. This irregularity may result in a pulse deficit, where the number of apical beats exceeds the number of radial pulses felt at the wrist.

A. Different blood pressures in the upper limbs may indicate conditions such as aortic dissection or arterial stenosis, but they are not typically associated with atrial fibrillation. Atrial fibrillation primarily affects the heart rhythm rather than blood pressure distribution.

B. Differences in upper and lower lung sounds may indicate conditions such as pneumonia or pleural effusion, but they are not specific to atrial fibrillation. Atrial fibrillation primarily affects the heart's electrical activity rather than respiratory findings.

C. Differences between oral and axillary temperatures may indicate localized variations in temperature, such as infection or inflammation, but they are not specific to atrial fibrillation. Atrial fibrillation primarily affects cardiac rhythm rather than body temperature regulation.