Disorders of Cardiac Conduction and Rhythm
Case Study 5:
Jack, an apartment superintendent, grabbed a quick cup of coffee and then put on his coat to shovel snow off the front sidewalk. He is 56 years old and has experienced two episodes of angina over the past 3 years. This time when he was shoveling the snow, he felt palpitations in his chest. It was as though his heart had stopped and then began to beat rapidly as if to catch up. Afraid of what he was feeling, he went inside and called for an ambulance. When the paramedics arrived, they took an ECG and told Jack he was going to be fine. He was taken to hospital to be seen by an emergency physician and was released later that afternoon.
1. The ECG taken by the paramedics showed Jack was experiencing premature ventricular contractions. In general terms, how do PVCs appear on an ECG? What factors contributed to the onset of PVCs in Jack’s situation?
2. Describe the physiologic events in PVC. How is cardiac output disrupted with the presence of PVCs?
3. Because of Jack’s history, his PVCs leave him at risk for events such as ventricular tachycardia or ventricular fibrillation. Compare and contrast these two arrhythmias. Why are they particularly dangerous?