Thirty to 50% of patients experiencing an inferior wall infarct may also have involvement of the right ventricle. Right ventricular infarctions seldom exist alone; they are almost always seen with an inferior infarct. The coronary artery involved is usually an occluded right coronary artery (RCA).

     The proximal segment of the RCA supplies the sinoatrial (SA) node and the right atrial wall; the middle segment supplies the lateral and inferior right ventricle (RV); and the posterior portion of the left ventricle, the inferior septum, inferior left ventricular wall and atrioventricular (AV) node are perfused by the distal segment of the RCA. A few patients (10%) may have a right ventricle that is supplied by the circumflex artery.

     When the inferior wall of the left ventricle is deprived of blood through RCA occlusion, it is reasonable to ask whether the right ventricle is also involved, since an RVI can present distinct treatment challenges for the paramedic.¹

EARLY PRACTICE
     In the early days of EMS, cardiac monitors were not standard equipment on all ambulances. In those services without cardiac monitors, myocardial infarctions were recognized through history and physical exam, and some MIs were missed. When monitors became available, most were three- or four-lead and were used for dysrhythmia recognition only. Medics were trained in dysrhythmia recognition and treatment, but not in 12-lead interpretation. The ability to recognize a myocardial infarction in the field through ECG monitoring came much later.

     Chest pain was treated with high- flow oxygen, nitroglycerin and morphine. Paramedics did not realize that nitroglycerin and morphine could complicate care in patients with RVI.

FAST FORWARD TO 2008
     Most ambulances are now equipped with 12-lead monitors and defibrillators, which also provide capnography, blood pressure monitoring and pulse oximetry, and 12-lead ECG monitoring is now standard of care for prehospital emergency services.²

     Paramedics are usually required to maintain current American Heart Association Advanced Cardiac Life Support training, and most have now been exposed, at least minimally, to 12-lead ECG monitoring and interpretation.

     The emphasis on cardiac care in the field has evolved from dysrhythmia recognition and treatment only to recognition and treatment of an evolving MI.

     Medics see more evolving MIs than fatal dysrhythmias, and they must be able to diagnose the regions of the heart affected and treat patients appropriately.