Right ventricular infarction. What is it and why should you care?
Depending on what you read, right ventricular infarct may complicate up to 40 or 50% of all inferior MIs.
Remember, when we say inferior MI or anterior MI we’re talking about the inferior wall of the left ventricle or the anterior wall of the left ventricle.
If you look at the typical patient’s coronary anatomy, the right coronary artery comes off of the aortic root and runs down the right side of the heart, supplying the right atrium, right ventricle, and the inferior wall of the left ventricle.
But where in the RCA is the occlusion located?
If it’s a proximal occlusion (high up in the RCA) then the occlusion may actually be affecting the right ventricle and the inferior wall of the left ventricle.
Why is this a problem? Simple.
Look at this cross section of the heart.
When compared to the left ventricle (which is essentially a muscular tube) the right ventricle is thinner and attaches to the left ventricle like a pocket.
Remember, the right ventricle is only responsible for pulmonary circulation (lower pressure) where as the left ventricle (higher pressure) has to pump blood to the entire body and back.
In the setting of right ventricular infarction, the right ventricle can become “stunned” and fail to pump blood effectively. It essentially becomes a conduit through which blood flows. When this occurs, the patient becomes highly dependent on central venous pressure to maintain adequate cardiac output.
Sometimes, this is referred to as being “pre-load dependent” which is a term that I find amusing. In the first place, it’s become a catch phrase, but more importantly, raise your hand if you’re not pre-load dependent!
Because patients with a stunned right ventricle are dependent on central venous pressure to maintain cardiac output, it can be dangerous to give these patients nitroglycerin, which is a potent vasodilator. Morphine can cause problems for the same reason.
Patients with right ventricular infarction (almost always associated with inferior wall MI) tend to start out with borderline blood pressures. This is due in part to right ventricular stunning, but also because inferior MI often stimulates the Bezold-Jarisch reflex, which leads to a state of hypervagotonia. It’s no accident that sinus bradycardia is the most common arrhythmia associated with inferior MI!
Granted, it’s possible for a proximal occlusion of the RCA to upset the blood supply to the SA node, which could cause sinus bradycardia, but the percentage of inferior MIs that present with sinus bradycardia is far higher than this phenomenon could explain.
It’s also worth mentioning that varying degrees of AV block are known to occur with inferior MI, usually with a narrow complex escape rhythm.
So how do you know if a patient with inferior MI has an associated right ventricular infarct? After all, it might change your treatment! Or should it?
In Part 2 we’ll discuss how to identify right ventricular infarction on the 12 lead ECG, and in Part 3 I’ll share my thoughts as to whether or not it’s necessary to apply electrodes to the right side of the patient’s chest.
Right ventricular infarction Part 1
Check out our video-based 12-lead ECG course at ECG Medical Training!