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
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.
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.
A 2002 study among emergency physicians and cardiologists revealed that a high percentage (76%) of cardiologists believed acquisition and transmission of 12-lead ECGs by paramedics is beneficial, and half believed that it is beneficial for paramedics to be able to interpret 12-lead ECGs in the field.3
While there is no evidence that early recognition of RVI by paramedics results in improved survival, some believe that early intervention in RVI can be important in morbidity and mortality in these patients.4 Research led by emergency physician Steven Moye found that early fibrinolysis in patients with left and right ventricular infarcts could improve their chances of survival.5 Although, since that study, emphasis has shifted from fibrinolysis to other therapies like stenting, it would seem that early recognition can be beneficial.
The right ventricle may recover more quickly than left ventricular tissue, possibly due to its relatively low workload and collateral perfusion from the left coronary artery.5
ALL MIs ARE NOT THE SAME
With the advent of prehospital 12-lead ECGs, paramedics are first taught to recognize ST segment changes along with abnormal T waves and Q waves, and to recognize lateral, inferior, posterior and anterior infarcts, and combinations of those.
The implications of standard management techniques, such as administration of nitroglycerin and other vasodilators in RVI patients, have only recently been addressed in paramedic education.