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Is my patient having an acute myocardial infarction?

Corona, Gyl Garren RN, CCNS, CCRN, MSN

CRITICAL care
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Test your knowledge of signs, symptoms, and ECG clues with these three case studies.

A patient with an acute myocardial infarction (MI) may not exhibit the classic signs and symptoms, so learn to recognize the many faces of myocardial ischemia. The initial 12-lead electrocardiogram (ECG) may not yield many clues; some changes aren't evident until 2 to 3 hours into the MI, and ST-segment elevation doesn't occur in all cases. Test your assessment skills and nursing knowledge with the following three case studies.

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The postoperative patient

Three days ago, Kate Dunbar, 74, was admitted with community-acquired pneumonia. At 6 a.m., she awakens with complaints of indigestion, nausea, and shortness of breath. She's diaphoretic and her heart rate is 112 and regular; BP, 100/68; and respirations, 28 and shallow. You call the health care provider and report your assessment findings. He orders a stat 12-lead ECG, supplemental oxygen at 4 liters/minute by nasal cannula, and serum cardiac markers.

Remember that some women having an MI don't experience the chest pain men typically report. Instead, women may have vague, atypical signs and symptoms such as indigestion, nausea, vomiting, fatigue, and shortness of breath.

Ms. Dunbar's ECG (below) shows 2-mm ST-segment elevation in leads II, III and aVF, indicating an acute ST-segment-elevation inferior-wall MI. (A subsequent right-sided ECG shows no evidence of right ventricular infarction.) The physician orders chewable aspirin and a nitroglycerin infusion at 5 mcg/minute and transfers Ms. Dunbar to the cardiac care unit for continuous monitoring and possible reperfusion therapy.

Figure

Figure

Her BP drops slightly (to 94/42) with the intravenous (I.V.) nitroglycerin, and her cardiac monitor continues to reveal sinus tachycardia without ectopy. Because the facility has a cardiac catheterization lab, Ms. Dunbar is started on a glycoprotein IIb/IIIa and unfractionated heparin and is sent to the lab for emergency cardiac catheterization and possible percutaneous coronary intervention.

The catheterization shows a 98% stenosis of the right coronary artery, so Ms. Dunbar undergoes percutaneous transluminal coronary angioplasty (PTCA) with endovascular stent placement. Her 12-lead ECG returns to normal limits, free from ST-segment elevations. She's transferred to the cardiac care unit and recovers uneventfully.

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The weary visitor

Gladys Leonard, a frequent patient in your unit, has a long history of heart failure. She says she's worried about her husband; his father and brother both died suddenly of heart attacks, and Mr. Leonard, 58, has just been diagnosed with hypertension and diabetes. He's a smoker, and he has a stressful job. These multiple risk factors and family history put him at risk for an acute MI. You know that Mr. Leonard will be visiting his wife during your shift, so you plan some cardiac teaching for him and his wife during the visit.

When Mr. Leonard arrives, you notice that his face is very flushed. Rubbing his chest, he tells you that he has pressure over his chest that goes to his jaw and back. He's had this pressure for the past hour and thinks it may be indigestion. You can see that he's short of breath and diaphoretic, classic MI symptoms.

You call for assistance and Mr. Leonard is immediately taken to the emergency department, where the staff documents these assessment findings: sinus tachycardia with a heart rate of 125; BP, 154/90, and respirations, 22 with supplemental oxygen at 4 liters/minute via nasal cannula. His 12-lead ECG (right) shows ST-segment elevation in leads V1, V2, V3, and V4, indicating an acute anteroseptal-wall MI.

Figure

Figure

Mr. Leonard is given chewable aspirin, 2 mg of I.V. morphine for pain, and sublingual nitroglycerin followed by an I.V. infusion. He has no contraindications to beta-blocker therapy, so he starts therapy with I.V. labetalol. Blood is drawn for cardiac markers, and the cardiac catheterization lab schedules Mr. Leonard for immediate angiography. Because he has no contraindications for a GP IIb/IIIa inhibitor, he starts I.V. therapy with abciximab.

In the catheterization lab, the cardiologist finds that Mr. Leonard's left anterior descending coronary artery has a high-grade stenosis, so he performs PTCA and inserts a stent. Mr. Leonard is transferred to the cardiac care unit, where he recovers without complications.

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The mom with heart block

Eugenia Lewis, 55, comes to the hospital with her adult daughter. Mrs. Lewis has been complaining of general malaise, indigestion, and nausea for the past 2 weeks but wouldn't come to the hospital until her daughter insisted. You obtain a 12-lead ECG, which shows significant Q waves and slightly inverted T waves in leads II, III, and aVF. Mrs. Lewis' cardiac rhythm is Mobitz II (type II second-degree atrioventricular block) with a ventricular rate of 44. Her BP is 98/50, her respirations are 18 and regular, and her breath sounds are clear.

Mrs. Lewis is diagnosed as having had a recent inferior-wall MI. To treat the heart block, she receives a temporary transvenous pacemaker. The clues to Mrs. Lewis' inferior-wall acute MI include the significant Q waves (0.04 second or more wide, with a depth 25% or more of the height of the next R wave), indicating myocardial necrosis, and slightly inverted T waves. The right coronary artery supplies blood to the sinoatrial and atrioventricular nodes in most people. Ischemia or necrosis affecting this area can lead to conduction defects and heart blocks.

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Education is muscle

As the population gets older, more people are living with heart disease. Because many people, especially women, experience atypical symptoms of myocardial ischemia and infarction, they may fail to recognize early signs of trouble. Teaching patients and the public to recognize symptoms of an MI prompts them to seek treatment before their hearts are severely damaged. Keeping your knowledge sharp means that when they do arrive at the hospital, you'll be ready to intervene promptly and appropriately.

Gyl Garren Corona is a patient-care specialist at Lehigh Valley Hospital Center in Allentown, Pa.

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SELECTED REFERENCES

Antman EM, et al. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction. Executive summary: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1999 Guidelines for the Management of Patients with Acute Myocardial Infarction). Circulation. 110(5):588–636, August 3, 2004.
Braunwald E, et al. ACC/AHA 2002 guideline update for the management of patients with unstable angina and non-ST-elevation myocardial infarction. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on the Management of Patients with Unstable Angina). Journal of the American College of Cardiology. 40(7):1366–1374, October 2, 2002.
Lansky AJ, et al. Percutaneous coronary intervention and adjunctive pharmacotherapy in women. A statement for health care providers from the American Heart Association. Circulation. 111(7):940–953, February 22, 2005.
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