The total study sample consisted of 13,663 greater Worcester residents hospitalized with AMI of whom 6.6% (n=905) developed cardiogenic shock. The mean age of the study sample was 68.9 years, 58.5% were men, and 95.2% were Caucasian.
Baseline Demographic and Clinical Characteristics
Patients who developed cardiogenic shock during hospitalization for AMI were significantly older, were more likely to be women, to have a do not resuscitate order, have a history of diabetes, heart failure, or MI, to present to greater Worcester hospitals with dyspnea, and develop a Q wave MI during hospitalization as compared to patients who did not develop cardiogenic shock (). Patients with cardiogenic shock had significantly lower blood pressure, total serum cholesterol, and estimated GFR findings at the time of hospital admission, but higher heart rates and serum glucose levels, than patients who did not develop shock.
To provide more contemporary insights into the characteristics of patients with AMI who were at risk for developing cardiogenic shock, we examined differences in these characteristics in patients hospitalized with AMI during our 3 most recent study years (); differences in the demographic characteristics of patients who did, as compared to those who did not, develop cardiogenic shock were no longer apparent whereas differences in previously observed clinical and physiologic factors remained.
Hospital Treatment Practices
Patients who developed cardiogenic shock during hospitalization for AMI were significantly less likely to be treated with aspirin, beta blockers, calcium channel blockers, and lipid lowering agents during hospitalization than patients who did not develop shock. Patients who developed cardiogenic shock were more likely to have been prescribed thrombolytic therapy, and to have undergone cardiac catheterization, coronary artery bypass surgery, and a PCI, than patients who did not experience cardiogenic shock (). Patients who developed cardiogenic shock were significantly more likely to have received mechanical support during hospitalization through intra-aortic balloon counterpulsation.
With specific regards to the elderly (≥65 years), those who developed cardiogenic shock were significantly less likely to have undergone cardiac catheterization (39.9%, 28.8%, 21.7%), a PCI (23.0%, 15.8%, 15.8%), coronary artery bypass surgery (7.0%, 6.0%, 0%), and received intra-aortic balloon counterpulsation (34.1%, 23.5%, 13.3%) with advancing age (65-74, 75-84, ≥85 years, respectively) (p<.001); similar age-related differences in the use of cardiac diagnostic and interventional procedures were observed in patients who did not develop cardiogenic shock.
In examining differences in the use of these treatment practices in patients who were hospitalized in our 3 most recent study years (), differences in the use of various treatment approaches either no longer remained apparent or became attenuated. The use of beneficial cardiac medications increased markedly over time in patients with AMI, irrespective of the development of cardiogenic shock. The use of thrombolytic therapy considerably declined in both patient groups during recent years while the use of PCI and intra-aortic balloon counterpulsation increased markedly.
Changing Trends in the Incidence Rates of Cardiogenic Shock
Between 1975 and the late 1980's, the incidence of cardiogenic shock remained relatively stable averaging approximately 7.5% over this period (). While the proportion of patients with AMI who developed cardiogenic shock during hospitalization was somewhat inconsistent thereafter, beginning in 1990 declines in the incidence rates of cardiogenic shock were observed reaching a nadir in incidence rates of 4.1% in 2003. Overall, there were significant changes in the frequency of cardiogenic shock complicating AMI during the years under study (p<0.01). Of the patients who developed cardiogenic shock, approximately 78% of these patients either presented with, or developed, this hemodynamic disturbance during the first day of hospitalization during our first 3 study years (1975/78/81) as compared to approximately 77% in our 3 most recent years under investigation.
Among the elderly, the overall incidence rates of cardiogenic shock did not vary appreciably (65-74 years 7.3%; 75-84 years 8.2%; ≥85 years 7.0%). In 2003 and 2005, the incidence rates of cardiogenic shock declined with advancing age (65-74 years 6.8%; 75-84 years 4.9%; ≥85 years 4.1%).
We carried out a series of regression analyses to examine differences from the baseline study year of 1975 in the rates of cardiogenic shock while controlling for several factors that might affect the likelihood of developing shock in patients with AMI (). The results of these analyses were similar to those of our unadjusted analyses of declines in the incidence rates of cardiogenic shock during the most recent years under investigation. Statistically significant declines in the proportion of patients with AMI who developed cardiogenic shock were noted during 2001, 2003, and 2005 (compared to the referent year of 1975). Similar, albeit attenuated, changes were observed in the risk of developing shock between 1997 and 2005 when information about whether the MI was an ST segment, or non ST segment, elevation MI was available as well as when data were collected about additional physiologic findings.
Hospital Case-Fatality Rates
Overall, 65.4% of patients with AMI who developed cardiogenic shock died during hospitalization in comparison to 10.6% of patients who did not develop cardiogenic shock (p<.001). In elderly patients with AMI, the overall hospital CFR's associated with cardiogenic shock increased with advancing age (65-74 years 65.1%; 75-84 years 75.8%; ≥85 years 75.2%).
A logistic regression analysis was carried out for purposes of examining the association between occurrence of cardiogenic shock and hospital CFR's while controlling for several demographic and clinical factors of prognostic importance. The results of this analysis confirmed the markedly higher risk of dying during hospitalization among patients who developed cardiogenic shock as compared to those who did not (adjusted O.R. = 17.8, 95% CI 14.5, 20.9). When we restricted our analysis to patients hospitalized during 2003 and 2005, patients with cardiogenic shock remained at markedly increased risk for dying during hospitalization in comparison to patients who did not develop cardiogenic shock, though the absolute risk of dying for patients with cardiogenic shock was considerably lower than during earlier study years (adjusted O.R. = 12.5; 95% CI 7.81,19.83).
In examining changing short-term death rates associated with cardiogenic shock (), in 1975/1978, 76.1% of patients who developed cardiogenic shock died in the hospital compared with 16.5% of patients who did not develop this complication. However, in 2003 and 2005, 45.4% of patients with shock died during hospitalization compared to 7.3% of patients who did not develop shock (p<.001) ().
Patients who developed cardiogenic shock during the most recent years under study were significantly less likely to have died in comparison to patients hospitalized with AMI in the 1970's and 1980's (). These trends were apparent irrespective of the demographic or clinical characteristics controlled for.
In 2003/2005, the hospital death rates associated with cardiogenic shock increased with advancing age in the elderly from 35.7% in patients 65-74 years to 57.1% and 64.7% in patients 75-84 and ≥85 years, respectively.
Since the length of hospital stay has markedly declined in our study population over the past 30 years (mean = 18 days in 1975; mean = 5 days in 2005), we examined changing trends in the 30 day CFR's after hospital presentation in patients who developed cardiogenic shock. The results of this analysis confirmed the declining short-term death rates in patients who developed cardiogenic shock over time. In 1975/78, the 30 day death rates after hospital admission for patients with cardiogenic shock were 20.7%; these death rates were 17.0% in 1990/91 and 12.8% in 2003/05.
Characteristics of Hospital Survivors With Cardiogenic Shock
Patients who survived an episode of cardiogenic shock were significantly younger, were less likely to have had a history of coronary disease or heart failure, were more likely to have higher diastolic blood pressure findings and higher levels of eGFR, and were more likely to have been treated with effective cardiac medications and interventional procedures than patients who died from cardiogenic shock (). Similar findings were observed when we compared patients who died from cardiogenic shock from those who survived this clinical syndrome in our 3 most recent study years.
Characteristics of Patients With Cardiogenic Shock Complicating Acute Myocardial Infarction (AMI) According to Hospital Survival Status