Recognition and Treatment of Right Ventricular Myocardial Infarction

FIELD DIAGNOSIS OF RVI
     Aside from questions about area of infarct, any patient who presents with chest pain, shortness of breath, unexplained hypotension, abdominal pain, back pain in the scapular or subscapular region, epigastric pain, neck or jaw pain, generalized weakness, syncope, complaint of tightness in the chest, nausea, vomiting, sweating (even in hyperthermic environments) that is unusual, and any other presentation that is systemically abnormal, should get an immediate 12-lead ECG. If 12-lead monitoring is available, failure to use it with such patients could result in liability.

     Cardinal signs of RVI are unexplained hypotension, distended jugular veins with Kussmaul's sign (increased jugular vein pressure on inspiration) and clear lung sounds;¹⁴ however, in the prehospital environment, it may be difficult to recognize these signs. The 12-lead ECG can be diagnostic, although not always. Some patients do not show ECG changes that are easy to recognize early in the evolution of an MI. Nevertheless, a 12-lead ECG should be done as soon as possible in patients with the above stated indications.¹⁵

     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. With RVI, the ECG may also show an acute anterior Q-wave pattern in leads V1 through V3.¹⁶ A significant Q wave is one that is >¼ the length of the following R wave, or wider than 0.03 seconds. (One small block on the ECG equals 0.04 seconds.)

     What is the significance of a right ventricular MI? The treatment of patients with RVI is different from non-RVI patients. If they are treated with nitroglycerin, they may experience sudden and dramatic hypotension from vasodilation.

     To acquire a regular left-sided 12-lead ECG, do the following:

     Begin by locating the patient's angle of Louis, which is the bony horizontal ridge between the upper part of the sternum, or manubrium, and the body of the sternum. From there, move your finger to the right into the depression between the second and third ribs. This is the second intercostal space. Work your finger down space by space until you reach the fourth intercostal space and place the normal V1 lead there, just to the right of the border of the sternum. Then, place V2 just across the sternum on the left margin, in the fourth intercostal space. Skip V3, move down and place V4 in the fifth intercostal space, midclavicular line. It is important to trace the midclavicular line down from the clavicle, which normally bisects the left nipple in males. Place V3 halfway between V2 and V4. Continue to palpate the fifth intercostal space and place V5 at the anterior axillary line and V6 in the mid-axillary line, still in the fifth intercostal space.

     After acquiring the normal left-sided ECG, leave the limb leads and electrodes for V1 and V2 where they are. (Note: Limb leads should be on the limbs, not the chest!) V2 now becomes lead V1R, and V1 becomes V2R. Switch the wires on those two leads accordingly. Place the remainder of the precordial (chest) leads on the right side of the chest in a mirror position from the left-sided 12-lead. Place V4R in the fifth intercostal space, midclavicular line; place V3R halfway between V2R and V4R; place V5R in the right fifth intercostal space, anterior axillary line; and place V6R in the fifth intercostal space, mid-axillary line.

     If the patient has large breasts, place the V3R lead on the breast and V4R and V5R leads below the breast.

     When the strip is printed, write "R" beside the V leads to mark that they are right leads, not left.

     It is important to place electrodes in the correct positions. Many ECG technicians rely on their experience, but that is not reliable. Electrode placement affects the reliability of the ECG, and care must be taken to place them properly. For example, if the limb leads are improperly placed on the chest, this must be noted on the ECG strip, because chest placement of limb leads can affect the tracing, which is important for the physicians interpreting the strip to know. If you change the position of limb leads or any other leads, this must also be written on the strip. Patterns can change if the patient's position is changed between ECGs. For example, moving the patient from a supine to a seated position can cause the tracings to look somewhat different. If the patient's position changed, note that on the strip for the interpreting physician. It is also good practice to leave the electrode pads in place when you transfer the patient to hospital care, since the new caregivers will be easily able to see that a right-sided ECG was done. This is especially helpful if there is commonality of equipment between the prehospital and emergency department providers. Leaving the electrodes in place allows the emergency department to obtain further EKGs from the same lead positions, reducing the chance of errors due to changes in position.