What feature in lead AVR makes it unreliable for assessing significant Q waves?

What feature in lead AVR makes it unreliable for assessing significant Q waves?

• A. It is positioned in a location that typically does not show infarction
• B. It always shows positive deflections
• C. It measures heart rate but not arrhythmias
• D. It reflects pulmonary pressure changes

Answer: (A)

Lead AVR (augmented vector right) is positioned on the right arm, and its location typically results in a perspective that is less favorable for detecting changes related to significant myocardial infarction. In the case of occlusion of the coronary arteries, significant Q waves – indicators of myocardial necrosis – are more likely to manifest in the leads that have a direct view of the left ventricle, such as leads V1 through V6 and the inferior leads like II, III, and aVF.

Since AVR looks at the heart from an unusual vantage point, it may not accurately reflect the presence of significant Q waves that arise from infarctions typically seen in the left heart territory. The anatomical positioning thus limits its reliability as it does not capture the electrical activity occurring in the regions more commonly affected by ischemia. This characteristic makes it difficult to draw conclusions about cardiac events solely from lead AVR.

The other features mentioned, such as the deflections in AVR or its role in measuring heart rate, do not contribute to its unreliability in assessing significant Q waves as directly as its anatomical position does.