Physiological Adaptation Q 78
Which of the following landmarks is the correct one for obtaining an apical pulse?
A. Left intercostal space, midaxillary line
B. Left fifth intercostal space, midclavicular line
C. Left second intercostal space, midclavicular line
D. Left seventh intercostal space, midclavicular line
Correct Answer: B. Left fifth intercostal space, midclavicular line
The correct landmark for obtaining an apical pulse is the left intercostal space in the midclavicular line. This is the point of maximum impulse and the location of the left ventricular apex.
Option A: Normally, heart sounds aren’t heard in the midaxillary line. During systolic contraction of the heart, a high amplitude wave of blood gets ejected through the aortic valve out towards the periphery. This high-pressure wave distends the arteries, especially compliant “elastic” or “conducting” arteries, which tend to be larger and closer to the heart. The subsequent release of that distention somewhat sustains the systolic wave of blood throughout the body, creating a spike followed by a downward sloping plateau in pulse waveform.
Option C: The left second intercostal space in the midclavicular line is where the pulmonic sounds are auscultated. The intensity of the pulse is determined by blood pressure as well as other physiological factors such as ambient temperature. For example, colder temperatures cause vasoconstriction leading to decreased intensity. Besides the normal variation in a rhythm that occurs with the respiratory cycle, the heart rate should be regular in the absence of pathology.
Option D: Heart sounds are not heard in the seventh intercostal space in the midclavicular line. Pulses are accurately measured when the clinician places their fingertips onto the skin overlying the vessel (locations, see below) and focuses on different aspects of the pulse. (NB: although one often hears that utilization of the thumb for measuring pulses is less accurate secondary to increased perception of the clinician’s own pulsation during palpation, the author could not find data to support or refute this claim). If possible, the limb under evaluation should have support throughout palpation.