On right ventricular MI

(As a general disclaimer, you should never go outside of your protocol or medical direction. Depending on what state you live in you could be decertified, brought into legal complications if possible actions cause patient harm, and you could harm a patient. The following discussion is being introduced as informative, and if you agree with it should be presented to your administration for their consideration, only after you yourself have vetted all information.) Also I meant this to be a small post, sorry it ran long.

I hear it too often, chest pain of possible cardiac origin, use nitroglycerin. On the whole it seems like a reasonable assumption. We reduce preload with nitroglycerin, we reduce the workload that the heart has and thus we reduce the oxygen consumption that is necessary from the myocardium. If it’s angina we may completely eliminate the problem, if it is not angina we will know it because the pain will not be relieved and we will also provide the heart with a slightly better possible outcome since we have done all of these beneficial things for the heart. If it is not angina we will still have reduced preload, reduced the myocardium workload, and reduced the hearts oxygen consumption.

There are a few contraindications to nitroglycerin use. The big ones we all know are not to use it with a patient that has taken Viagra or other ED medications within 24 hours. We know not to use nitro with a patient that is hypotensive because of possible further lowering of the blood pressure. Obviously if the patient is allergic to nitro we can’t use it on them. There is another small but very important precaution for it’s use and that is that it should not be used with patients that have a right ventricular MI.

The reason we should not use nitroglycerin with a patient that is having a right sided ventricular MI is that according to William E. Gandy at EMSWORLD:

The right ventricle is not designed to provide systemic circulation. Its purpose is to pump blood through the lungs and pulmonary circuit. Thus, the pressures it is required to produce are less, and it has a thinner wall than the left ventricle, which must pump blood throughout the body.

Its functional abilities are dependent upon preload, or the volume of venous return to the heart, principally during diastole, since veins do not have muscular walls to keep blood moving as do the arteries. The right atria and ventricle have relatively little “suction” from contractions to pull blood into them.

So a reduction in venous return will result in diminished pumping pressure by the right ventricle, diminished pulmonary circulation, diminished left ventricular filling, diminished cardiac output, diminished systemic blood pressure and, if not corrected, possible dysrhythmias, shock and death.

All of this because we followed our protocol and administered nitroglycerin to a patient with chest pain.

So first how can we ever determine if the MI is right ventricular in nature?

The first classic sign is hypotension. Consider most patients that complain of extreme chest pain, many times the pain alone can cause the elevation in blood pressure. If that elevation is absent or actually becoming hypotensive and we don’t see the patient taking medications that may lower it, such as beta blockers, we may be able to begin to see signs of a right sided ventricular MI.

12 lead ECG monitoring has steadily been receiving more and more importance in early detection. It is true that on a standard ECG we can’t see right ventricular MIs. What we can do is figure out when to “suspect” them.

Quick note on 12 leads: if you have the ability to do 12 leads do them on all patients that require them. Do them and do them often. It is not only a skill reading them, it is also a skill obtaining them. I have seen doctors and nurses fumble on obtaining them. I have also seen techs get such a clear and quick 12 lead it would surprise you. I’m not saying one person is smarter or better than the other. I am saying practicing this skill can dramatically decrease your time in obtaining a 12 lead. Also it doesn’t take long to obtain the 12 lead. It does take long if you don’t know which pocket on the monitor you have the 12 lead cables, once you find the cables they don’t have the electrodes attached, and now you can’t find the electrodes. With practice you can finish a 12 lead in about the amount of time it takes your partner to prep an IV bag.

If we see ST elevation indicating an inferior MI, which would be ST elevation in leads 2, 3, and avf we should consider a right side MI and do a right sided 12 lead.

A 12-lead tracing that shows ST segment elevation in any of the inferior leads (II, III or aVF), or relative ST segment depression in V2 or V3 compared with lead V1, should immediately trigger acquisition of a right-sided 12-lead (Gandy)
In a standard 12 lead we would place the limb leads on the limbs, V1 would go on the 4th intercostal space just right of the sternum, V2 on the 4th intercostal space just left of the sternum, V3 between V2 and V4, V4 on the 5th intercostal space midclavicular line, V5 level with V4 anterior axillary, V6 midaxillary level with V5.

On a right sided 12 lead we would place V1 where V2 normally goes, V2 where V1 normally goes and the rest of the leads using the same landmarks you would use only on the right side of the chest. Thus V4 would go 5th intercostal space Right midclavicular. V3 between V2 and V4. V5 level with V4 anterior axillary, V6 Right midaxillary level with V5.

(I will attach a picture of what I described above but I do not own the rights to it so I may have to remove it.)

Once we have obtained the right sided 12 lead we can look for ST elevation in V4. If we see ST elevation in V4 a right sided MI can be diagnosed. At the very minimum we should contact medical control and advise them of possible right sided MI and request specific orders. Hypotension should be combated both with fluid resuscitation as well as dobutamine or dopamine if dobutamine is not available. Of course fluid resuscitation should be done with careful monitoring of lung sounds as pulmonary edema should be avoided.

I hope I have helped shed some light on right sided MIs and I will be posting link below to a great online article on the subject. AMLS also has some great information on the subject and that is where I got the picture I posted above as well as some of the information in this article. It was in an AMLS class I first completely understood right sided MIs. I highly encourage medics to take that class.

Any questions or comments feel free to drop me a line as a comment or email me.

EMS World. Recognition and treatment of right sided MI

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