Case 6: A 46 year old man with right shoulder pain and dyspnea. History of alcoholism. No prior cardiopulmonary disease history.
Thought 1. What best explains all of the abnormalities in this ECG?
Thought 2. Does the ECG play a role in immediately establishing a differential for the patient's problem?
Findings in this ECG are suggestive of Right ventricular hypertrophy, it allows for expeditious diagnosis and appropriate treatment.
The best way to understand all of this ECG's messages is to analyze it systematically, like one should all tracings. That is, calculate rate, rhythm, axis, intervals and then look for morphologic abnormalities. The rate indicates sinus tachycardia (P-waves are upright in Leads II, III, and aVF). The vector of QRS depolarization determined from the limb leads is called the frontal plane axis. It is abnormal in this ECG.
Let's figure out the axis. First, look at Leads I and aVF to determine to which quadrant the QRS vector is directed.
The Synthesis of a QRS Frontal Plane Axis: If a QRS is primarily negative in a given lead, the vector has to be directed away from that lead and the axis then has to occupy the half circle opposite the lead (note shaded area below).
Ifa QRS is primarily positive in a given lead, the vector has to be directed towards that lead and the axis then has to occupy the half circle in the direction of the lead (note shaded area, above left).
The frontal plane axis therefore is in the inferior and right quadrant (from +90 to +120...). This is called right axis deviation (note the darker red shaded area, above right). The estimation of the QRS axis can be further refined by looking for a lead in which the QRS is nearly equal positive and negative. Since the QRS is equally positive and negative in Lead II, the QRS vector is perpendicular to Lead II. This means that the QRS axis in this tracing is approximately +150.
There aren't many abnormalities that result in this significant of a right axis in an adult. They include right ventricular hypertrophy (RVH), left posterior fascicular block and dextrocardia, amongst others.
The remainder of the clues are in Leads V1 and V6.
The tall R-wave in V1 and the persistent S-wave in V6, along with right axis deviation indicate the presence of RVH. (The ST and T abnormalities can all be secondary to the RVH.)
With no prior history of cardiopulmonary disease, you should immediately wonder if this ECG represents an acute right ventricular problem, something you'd expect primarily from an acute pulmonary event. Indeed a stat echo showed RV enlargement, with leftward deviation of the interventricular septum and an inferred pulmonary systolic pressure of 64mmHg.
Note the large defect on the patient's perfusion lung scan, rendering the scan a high probability for acute pulmonary embolus.
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