Myocardial Infarction: Prognosis and Predictors of Mortality
A person who has experienced myocardial infarction (MI) is likely to experience other cardiovascular events. During the first 30 days after a myocardial infarction, death can occur due to cardiogenic shock, sudden cardiac death, heart failure, mechanical cardiac complications, or another MI event. However, due to recent developments in reperfusion techniques, in-hospital death rates have decreased from 5.3% to 3.8%.1 The goal of reperfusion interventions is to limit the amount of permanent myocardial damage, necrosis, and scar tissue formation.2-5
In ST-elevation myocardial infarction (STEMI), the increased use of fibrinolytic therapy and primary percutaneous intervention (aka angioplasty with stent), in conjunction with the increased use of aspirin, ACE inhibitors, statins and beta-blockers, has improved mortality rates.5 Thirty day mortality rates are 13% with medical therapy alone, 6-7% with optimal fibrinolytic therapy, and 3% to 5% with primary percutaneous coronary intervention when performed within 2 hours of hospital arrival.6-9 There is an even lower risk of death of only 2% in patients with non-ST elevation myocardial infarction (NSTEMI) after 30 days, as compared to STEMI.10-11 The utilization of early invasive reperfusion techniques in NSTEMI patients will likewise decrease MI recurrence, rehospitalization and mortality.
The risk of death after a myocardial infarction is determined by understanding the predictors of mortality. Risk scores gauge the outcome after an acute MI. The most commonly used scoring system is the TIMI risk scores for STEMI and NSTEMI.12-13 The higher the score, the more the patient is at risk of mortality from cardiac events (Table 1 and Table 2).
Table 1. Thrombolysis in myocardial infarction (TIMI) score for ST elevation acute myocardial infarction (STEMI).
TIMI risk score : 0 points (0.8%); 1 point (1.6%); 2 points (2.2%); 3 points (4.4%); 4 points (7.3%); 5 points (12%); 6 points (16 %); 7 points (23%); 8 points (27%); 9-14 points (36.0%).
Table 2. Thrombolysis in Myocardial Infarction (TIMI) score for unstable angina or non ST elevation myocardial infarction (NSTEMI).
TIMI risk scores: 0-1 points (3% to 5%); 2 points (3% to 8%); 3 points (5% to 13%); 4 points (7% to 20%); 5 points (12 % to 26%); 6-7 points (19% to 41%).
A common complication of myocardial infarction is ischemic mitral regurgitation, which is due to infarction with annulus dilatation or displacement of the papillary muscle secondary to changes within the left ventricular anatomy following a cardiovascular event. The risk of death is more pronounced in patients with moderate to severe mitral regurgitation compared to mild mitral regurgitation.14
As mentioned earlier, patients with a history of myocardial infarctions are likely to have a recurrent MI. They have an increased risk for complications and death, especially if the location of the next infarct is far from the previous cardiac event.15
Normal coronary arteries or no vessel with ≥50% stenosis is observed in 12% to 14% of patients with NSTEMI and 7.5% of patients with STEMI.10-11 Collectively, they are known as MI with normal coronary arteries. These may be due to rapid clot lysis, vasospasm, or coronary microvascular disease. The risk of death in these patients is lower than those with a culprit lesion.
Left bundle branch block (LBBB) and right bundle branch block (RBBB) often precede MI. The risk of mortality is increased in these patients. Bundle branch block progresses to second or third degree AV block.16-18 Also, these patients tend to have more comorbidities such as hypertension, diabetes, and stroke.17
The experience of the clinician managing the patient with MI affects patient survival.19-20 Patient survival is significantly increased if the clinician handles more than 24 MI cases per year (19.6% patient mortality per year), as compared to clinicians who handle less than 5 MI patients per year (24.2% patient mortality per year).19 Myocardial infarction patients cared for by a cardiologist have lower mortality than those cared for by other clinicians.20 Hospital experience is also a factor in survival of myocardial infarction patients. Studies have found that patients admitted to hospitals with a low volume of MI patients had a higher risk of mortality, as compared to patients admitted to hospitals with high MI patient volume (hazard ratio = 1.17; 95% CI 1.09-1.26).21
Considering gender, short term (in-hospital/30-day) mortality and long term mortality after myocardial infarction is higher in women compared to men; this is observed in younger women less than 55 years old.22-24 However, the difference declines as patients get older.25
In summary, we have learned that patients who survive myocardial infarction are at risk of developing further cardiac events and are at increased risk for mortality. The prognosis of the individual depends on the predictors of mortality listed above.
- Myerson M, Coady S, Taylor H, et al. Declining severity of myocardial infarction from 1987 to 2002: the Atherosclerosis Risk in Communities (ARIC) Study. Circulation 2009; 119:503.
- Rosamond WD, Chambless LE, Folsom AR, et al. Trends in the incidence of myocardial infarction and in mortality dueto coronary heart disease, 1987 to 1994. N Engl J Med 1998; 339:861.
- Furman MI, Dauerman HL, Goldberg RJ, et al. Twenty-two year (1975 to 1997) trends in the incidence, in-hospital and long term case fatality rates from initial Q-wave and non-Q-wave myocardial infarction: a multi-hospital, community-wide perspective. J Am Coll Cardiol 2001; 37:1571.
- Rogers WJ, Canto JG, Lambrew CT, et al. Temporal trends in the treatment of over 1.5 million patients with myocardial infarction in the US from 1990 through 1999: the National Registry of Myocardial Infarction 1, 2, and 3. J Am Coll Cardiol 2000; 36: 2056.
- Heidenreich PA, McClellan M. Trends in the treatment and outcomes for acute mtocardial infarction: 1975-1995. Am J Med 2001; 110:165.
- An international randomized trial comparing thrombolytic strategies for acute myocardial infarction. The GUSTO investigators. N Engl J Med 1993; 329:673.
- Assessment of the safety and efficacy of a new thrombolytic (ASSENT-2) Investigators, Van De Werf F, Adgey J, et al. Single bolus tenecteplase compared with front-loaded alteplase in acute myocardial infarction: ASSENT-2 double-blind randomized trial. Lancet 1999; 354:716.
- Cannon CP, Gibson CM, Lambrew CT, et al. Relationship of symptom-onset-to-balloon time and door-to-balloon time with mortality in patients undergoing angioplasty for acute myocardial infarction. JAMA 2000; 283:2941.
- Stone GW, Grines CL, Cox DA, et al. Comparison of angioplasty with stenting, with or without abciximab, in acute myocardial infarction. N Engl J Med 2002; 346:957.
- Invasive compared with non-invasive treatment in unstable coronary-artery disease: FRISC II prospective randomized multicenter study. FRagmin and Fast Revascularization during InStability in Coronary artery disease Investigators. Lancet 1999; 354:708
- Cannon CP, Weintraub WS, Demopoulos LA, et al. Comparison of early invasive and conservative strategies in patients with unstable coronary syndromes treated with the glycoprotein IIB/IIIa inhibitor tirofiban. N Engl J Med 2001; 334:1879.
- Law MR, Watt HC, Wald NJ. The underlying risk of death after myocardial infarction in the absence of treatment. Arch Intern Med 2002; 162:2405.
- Antman EM, Cohen M, Bernink PJ, et al. The TIMI risk score for unstable angina/non-ST elevation MI: A method for prognostication and therapeutic decision making. JAMA 2000;284:835.
- Bursi F, Enriquez-Sarano M, Nkomo VT, et al. Heart failure and death after myocardial infarction in the community: the emerging role of mitral regurgitation. Circulation 2005; 111:295.
- Shotan A, Gottlieb S, Goldbourt U, et al. Prognosis of patients with a recurrent acute myocardial infarction before and in the reperfusion era—a national study. Am Heart J 2001:141:478.
- Dubois C, Pierard LA, Smeets JP, et al. Short- and long-term prognostic importance of complete bundle branch block complicating acute myocardial infarction. Clin Cardiol 1998; 11:292
- Hindman MC, Wagner GS, JaRo M, et al. The clinical significance of bundle branc block complicating acute myocardial infarction. 1. Clinical characteristics, hospital mortality, and on-year follow-up. Circulation 1978; 58:679.
- Go AS, Barron HV, Rundle AC, et al. Bundle-branch block in-hospital mortality in acute myocardial infarction. National Registry of Myocardial Infarction 2 Investigators. Ann Intern Med 1998; 129:690.
- Tu JV, Austin PC, Chan BT. Relationship between annual volume of patients treated by admitting physician and mortality after acute myocardial infarction. JAMA 2001; 285:3116.
- Casale PN, Jones JL, Wolf FE, et al. Patients treated by cadiolodists have a lower in-hospital mortality for acute myocardial infarction. J Am Coll Cardiol 1998; 32:885.
- Thiemann DR, Coresh J, Oetgen WJ, Powe NR. Outcome of acute myocardial infarction according to specialty of admitting physician. N Engl J Med 1996; 335:1880.
- Greenland P, Reicher-Reiss H, Goldbourt U, Behar S. In-hospital and 1-year mortality in 1,524 women after myocardial infarction. Comparison with 4,315 men. Circulation 1991; 83:484.
- Gottlieb S, Harpaz D, Shotan A, et al. Sex differences in management and outcome after acute myocardial infarction in the 1990s: A prospective observational community-based study. Israeli Thrombolytic Survey Group. Circulation 2000; 102:2484.
- Vaccarino V, Parsons L, Every NR, et al. Sex-based differences in early mortality after myocardial infarction. National Registry of Myocardial Infarction 2 Paricipants. N Engl J Med 1999; 341:217.
- Berger JS, Elliot L, Gallup D, et al. Sex differences in mortality following acute coronary syndromes. JAMA 2009; 302:847.