Question

Amy, a 34-year-old female, delivered a healthy baby at 39 weeks of gestation with an uncomplicated vaginal delivery following spontaneous initiation of labor. Her pregnancy was normal, and she did not experience any hypertensive episodes during the three trimesters. Her child, a baby boy, was a healthy weight at birth and was breast-feeding normally. Ten days following the birth, Amy was recovering well; her blood pressure was 120/80 mm Hg. This was Amy’s second pregnancy and birth. During her first pregnancy, she did experience preeclampsia and was treated accordingly.

Three weeks postpartum, Amy was shopping and felt transiently ill when she lifted her three-year-old son. Immediately following, there was an onset of sudden left jaw and substernal pain. She traveled home and called emergency medical services (EMS). As a physician, Amy suspected that she was suffering from either severe heartburn or perhaps a pulmonary embolism. Upon evaluation, her pain resolved and emergency personnel left, as Amy determined that the most likely cause for the pain was heartburn. Soon thereafter, the pain recurred, and EMS was once again called.

Upon a second evaluation, Amy reported her pain at a level 5 (0 to 10, where 10 is most severe) and the onset of pain at a level of 7. Her blood pressure was 148/74 mm Hg. An electrocardiogram (ECG) revealed a normal sinus rhythm ranging from 90-100 beats per minute and an ST-segment elevation of 4 mm in leads V3 to V6. Doctors suspected that Amy was suffering from a myocardial infarction and administered supplemental oxygen, nitroglycerin (vasodilator), and morphine (analgesic). Her pain soon resolved. Amy did not complain of diaphoresis (excessive sweating), nausea, vomiting, dyspnea (shortness of breath), pain or edema (swelling) in the legs, or back pain. She reported living at her home with her husband, toddler, and newborn. She had no history of alcohol, tobacco, or illicit drug use. She was taking no medications and had no allergies. Family history revealed that her parents both had hypertension and hypercholesterolemia. In addition, she did have a distant cousin that suffered a stroke at a young age. Amy was transferred to Massachusetts General Hospital for further evaluation.

Upon arrival, Amy’s temperature was 97.2°F, blood pressure 143-92 mm Hg in the left arm and 137/81 mm Hg in the right arm, pulse 83-92 beats per minute, respiratory rate 20 breaths per minute, and oxygen saturation 95% while breathing ambient air. A chest radiograph revealed no abnormalities. Doctors repeated an ECG, which did confirm the ST-segment elevation found during her initial evaluation. In addition, doctors concluded that Amy had a possible left atrial enlargement and incomplete right-bundle branch block.

While Amy was undergoing evaluation, she continued to experience episodes of substernal pain, each lasting approximately 5 minutes. During these episodes, ECG changes were evident and then completely resolved. Doctors performed a differential diagnosis to determine the cause of Amy’s periodic substernal pain.

2 Nitroglycerin is an organic nitrate that promotes the production of nitric oxide, a widespread vasodilator. Justify the administration of nitroglycerin for Amy’s suspected myocardial infarction. Be sure to describe how nitroglycerin impacts resistance and blood flow through vessels.

Answer 1

Nitroglycerin is a potent vasodilator . It's mechanism of action :-

Nitrates and nitrites dilate arterioles and veins in the periphery (and coronary arteries in high doses); The resultant reduction in preload, and to a lesser extent afterload, decreases the workload of the heart and lowers myocardial oxygen demand; Act directly on smooth muscle walls of the arterioles, veins, or both, relaxing them; Lowers peripheral resistance, lowering blood pressure