Abstract
Background
Previous studies have demonstrated that acute myocardial infarction (AMI) in young patients (age <45 years) is associated with a high prevalence of smoking, obesity, hyperlipidemia and single vessel coronary artery disease (CAD). Hispanics represent the largest growing ethnic minority in the United States, yet features of AMI in young Hispanics have not been described.
Methods
Patients undergoing percutaneous coronary intervention for AMI at Los Angeles County + University of Southern California Medical Center and Keck Medical Center were studied. We compared young Hispanics (age < 45, n = 47) with older patients (Hispanics and non-Hispanics age ≥45, n = 888) to identify unique features of AMI in young Hispanics. We also compared young Hispanics with young non-Hispanics (n = 33) and older Hispanics (n = 447) in regards to traditional CAD risk factors, laboratory values and in-hospital outcomes. Multivariable logistic regression was performed to identify variables independently associated with in-hospital mortality.
Results
Young Hispanics had higher triglyceride levels than young non-Hispanics and older patients (234.5 ± 221.0 mg/dL vs. 145.3 ± 67.4 mg/dL vs. 156 ± 118.2 mg/dL, p < 0.0004); and higher triglyceride than older Hispanics (234.5 ± 221.0 vs. 147.0 ± 98.9 mg/dL, p < 0.02). Body mass index was independently associated with the logarithm (base10) of triglyceride levels (p < 0.0001). Hispanic ethnicity and age < 45 years, however, were not independently associated with in-hospital mortality.
Conclusions
Young Hispanics with AMI have higher triglyceride levels than young non-Hispanics and older Hispanics. The elevated triglyceride levels may be related to lifestyle changes experienced by a young immigrant population transitioning to life in the United States.
Highlights
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Features of acute myocardial infarction (AMI) in young Hispanics were studied.
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Young Hispanics were compared to young non-Hispanics and older Hispanics.
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Young Hispanics with acute MI have higher triglyceride levels than other patients.
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This finding may be related to lifestyle changes experienced by young Hispanics.
1
Introduction
Young patients (<45 years of age) presenting with AMI have a cardiovascular disease (CVD) risk profile that is distinct from that of older patients . Specifically, smoking, obesity and hyperlipidemia are more common among young patients . Traditional comorbid conditions, however, including hypertension, diabetes mellitus and previously established coronary artery disease (CAD), are less prevalent in this patient population . Previous studies have also demonstrated a higher likelihood of single vessel CAD and lower rates of in-hospital morbidity and mortality when young patients with AMI are compared with older patients .
The relatively few studies that have focused on CAD in Hispanics, have shown that overall Hispanics have a high prevalence of diabetes mellitus, obesity, elevated triglyceride levels and metabolic syndrome . CAD in young Hispanics however has not previously been described. We therefore sought to identify unique risk factors and clinical characteristics associated with AMI in young Hispanics.
2
Methods
The study population was composed of patients who presented with AMI and underwent percutaneous coronary intervention (PCI) at Los Angeles County + University of Southern California (USC) Medical Center and Keck Medical Center of USC between January 2008 and December 2012. Patients with both ST segment elevation myocardial infarction (STEMI) or non-ST elevation MI (NSTEMI), undergoing coronary angiography and PCI, were included in the study cohort. Patients who were asymptomatic or who presented with abnormal cardiac stress tests, stable angina, unstable angina or worsening congestive heart failure without elevated cardiac enzymes or ECG findings consistent with STEMI or NSTEMI were excluded from the study. Informed consent was obtained from all patients. Triglyceride and hemoglobin A 1c levels were measured upon admission to the coronary care unit following PCI. The Institutional Review Board at the University of Southern California approved this study. Pre-specified clinical and laboratory data and clinical events were obtained from hospital charts reviewed by independent research personnel blinded to the objectives of the study. A dedicated data coordinating center performed all data management and analyses.
Bleeding complications were defined as at least one of the following events during the index hospitalization: access site hematoma (>10 cm diameter), retroperitoneal bleeding, gastrointestinal bleeding, or bleeding with a decrease in hemoglobin requiring blood transfusion. Acute renal failure was defined as an absolute increase in baseline creatinine greater than 0.5 mg/dL. In-hospital morbidity was defined as any of the following complications: bleeding complications, acute renal failure, vascular complications, abrupt culprit vessel closure, neurologic complications (transient ischemic attack or stroke), ischemic complications (recurrent chest pain, new ischemic electrocardiographic changes, arrhythmia, or urgent repeat coronary angiography). Metabolic syndrome was defined as ≥3 of the following, in accordance with the National Cholesterol Education program definition: triglycerides >150 mg/dL, HDL <50 mg/dL for females or HDL <40 mg/dL for males, hypertension, BMI ≥30 kg/m 2 , and fasting glucose >100 mg/dL without previous diagnosis of diabetes mellitus . Race and ethnicity were self-reported by each patient at the time of hospital admission. Patients identified themselves as Hispanic, African-American, Caucasian, Asian, Native American, or other and could only select one ethnicity. Patients were then categorized as Hispanic or non-Hispanic for purposes of comparison. Patients were categorized as young if their age was <45 years. Young Hispanic patients were then compared to older patients (Hispanics and non-Hispanics combined), to identify differences between young Hispanics and older patients. Young Hispanics were also compared to young non-Hispanics and older Hispanics (age ≥ 45 years) to elucidate features of AMI that may be associated with Hispanic ethnicity.
Continuous variables are presented as mean ± standard deviation and categorical variables as number and percentage. Differences in continuous variables between groups were evaluated with either the Student t-test or Wilcoxon rank sum test. Categorical variables were compared between groups using the Chi-square test or Fisher’s exact test. A p value <0.05 was considered statistically significant. A multivariable logistic regression model was constructed to identify covariables independently associated with in-hospital mortality. Covariables were selected based upon significant univariable p values and overall clinical relevance. Covariables included in the model were: presentation with cardiogenic shock, history of diabetes mellitus, left anterior descending artery (LAD) culprit lesion, and Hispanic ethnicity with age < 45 years. A multivariable linear regression model was also generated to identify variables associated with triglyceride levels. Although triglyceride level was the outcome variable, the logarithm (base 10) of triglycerides was used in the model as triglyceride values were not normally distributed. Covariables included in this regression were: history of diabetes mellitus, BMI, Hispanic ethnicity, age < 45 years, and the interaction term between Hispanic ethnicity and age < 45.
2
Methods
The study population was composed of patients who presented with AMI and underwent percutaneous coronary intervention (PCI) at Los Angeles County + University of Southern California (USC) Medical Center and Keck Medical Center of USC between January 2008 and December 2012. Patients with both ST segment elevation myocardial infarction (STEMI) or non-ST elevation MI (NSTEMI), undergoing coronary angiography and PCI, were included in the study cohort. Patients who were asymptomatic or who presented with abnormal cardiac stress tests, stable angina, unstable angina or worsening congestive heart failure without elevated cardiac enzymes or ECG findings consistent with STEMI or NSTEMI were excluded from the study. Informed consent was obtained from all patients. Triglyceride and hemoglobin A 1c levels were measured upon admission to the coronary care unit following PCI. The Institutional Review Board at the University of Southern California approved this study. Pre-specified clinical and laboratory data and clinical events were obtained from hospital charts reviewed by independent research personnel blinded to the objectives of the study. A dedicated data coordinating center performed all data management and analyses.
Bleeding complications were defined as at least one of the following events during the index hospitalization: access site hematoma (>10 cm diameter), retroperitoneal bleeding, gastrointestinal bleeding, or bleeding with a decrease in hemoglobin requiring blood transfusion. Acute renal failure was defined as an absolute increase in baseline creatinine greater than 0.5 mg/dL. In-hospital morbidity was defined as any of the following complications: bleeding complications, acute renal failure, vascular complications, abrupt culprit vessel closure, neurologic complications (transient ischemic attack or stroke), ischemic complications (recurrent chest pain, new ischemic electrocardiographic changes, arrhythmia, or urgent repeat coronary angiography). Metabolic syndrome was defined as ≥3 of the following, in accordance with the National Cholesterol Education program definition: triglycerides >150 mg/dL, HDL <50 mg/dL for females or HDL <40 mg/dL for males, hypertension, BMI ≥30 kg/m 2 , and fasting glucose >100 mg/dL without previous diagnosis of diabetes mellitus . Race and ethnicity were self-reported by each patient at the time of hospital admission. Patients identified themselves as Hispanic, African-American, Caucasian, Asian, Native American, or other and could only select one ethnicity. Patients were then categorized as Hispanic or non-Hispanic for purposes of comparison. Patients were categorized as young if their age was <45 years. Young Hispanic patients were then compared to older patients (Hispanics and non-Hispanics combined), to identify differences between young Hispanics and older patients. Young Hispanics were also compared to young non-Hispanics and older Hispanics (age ≥ 45 years) to elucidate features of AMI that may be associated with Hispanic ethnicity.
Continuous variables are presented as mean ± standard deviation and categorical variables as number and percentage. Differences in continuous variables between groups were evaluated with either the Student t-test or Wilcoxon rank sum test. Categorical variables were compared between groups using the Chi-square test or Fisher’s exact test. A p value <0.05 was considered statistically significant. A multivariable logistic regression model was constructed to identify covariables independently associated with in-hospital mortality. Covariables were selected based upon significant univariable p values and overall clinical relevance. Covariables included in the model were: presentation with cardiogenic shock, history of diabetes mellitus, left anterior descending artery (LAD) culprit lesion, and Hispanic ethnicity with age < 45 years. A multivariable linear regression model was also generated to identify variables associated with triglyceride levels. Although triglyceride level was the outcome variable, the logarithm (base 10) of triglycerides was used in the model as triglyceride values were not normally distributed. Covariables included in this regression were: history of diabetes mellitus, BMI, Hispanic ethnicity, age < 45 years, and the interaction term between Hispanic ethnicity and age < 45.
3
Results
Young Hispanics had higher triglyceride levels than young non-Hispanics and older patients (234.5 ± 221.0 mg/dL vs. 145.3 ± 67.4 mg/dL vs. 156 ± 118.2 mg/dL, p = 0.004). Young Hispanics also had higher total cholesterol and non-HDL cholesterol than the other 2 groups (202.5 ± 65 mg/dL vs. 175.3 ± 48.2 mg/dL vs. 173.2 ± 53.4 mg/dL, p = 0.003 and 164.2 ± 65.9 mg/dL vs. 135.8 ± 46.1 mg/dL vs. 132.4 ± 51.5 mg/dL; p = 0.0007 respectively; Table 1 ). Low density lipoprotein (LDL) and high density lipoprotein (HDL) levels were similar in young Hispanics, young non-Hispanics and older patients (118.0 ± 52.1 mg/dL vs. 106.3 ± 41.2 mg/dL vs. 104 ± 54.6 mg/dL p = 0.27; and 38.3 ± 12.2 mg/dL vs. 39.5 ± 12.8 mg/dL vs. 40.8 ± 13.5 mg/dL; p = 0.46, respectively; Table 1 ).
| Hispanic <45 years (n = 47) | Non-Hispanic <45 years (n = 33) | Hispanic + Non-Hispanic >45 years (n = 888) | p Value | |
|---|---|---|---|---|
| Age, years | 39.2 ± 6.7 | 37.6 ± 8.6 | 61.5 ± 10.0 | <0.0001 |
| Male | 41 (87.2%) | 30 (90.9%) | 678 (76.4%) | 0.03 |
| Obesity (BMI ≥30 kg/m 2 ) | 13 (27.7%) | 12 (36.4%) | 245 (27.6%) | 0.54 |
| BMI (kg/m 2 ) | 29.5 ± 4.4 | 35.2 ± 23.0 | 28.9 ± 9.7 | 0.005 |
| Current smoker | 18 (38.3%) | 12 (36.4%) | 195 (22.0%) | 0.008 |
| Diabetes mellitus | 15 (31.9%) | 4 (12.1%) | 344 (38.7%) | 0.004 |
| Metabolic syndrome | 28 (59.6%) | 24 (72.7%) | 379 (42.7%) | 0.0003 |
| Hypertension | 24 (51.1%) | 13 (39.4%) | 657 (74.0%) | <0.0001 |
| Dyslipidemia | 25 (53.2%) | 13 (39.4%) | 509 (57.3%) | 0.07 |
| Chronic kidney disease | 1 (2.1%) | 1 (3.0%) | 89 (10.0%) | 0.07 |
| Family history of coronary artery disease | 8 (17.0%) | 8 (24.2%) | 169 (19.0%) | 0.81 |
| Prior coronary artery bypass graft | 0 | 1 (3.0%) | 44 (5.0%) | 0.31 |
| Prior myocardial infarction | 5 (10.6%) | 0 | 152 (17.1%) | 0.007 |
| Prior PCI | 4 (8.5%) | 4 (12.1%) | 149 (16.8%) | 0.30 |
| Chronic obstructive pulmonary disease | 0 | 13 (39.4%) | 34 (3.8%) | 0.35 |
| History of CVA | 2 (4.3%) | 0 | 45 (5.1%) | 0.57 |
| Clinical presentation | ||||
| STEMI | 27 (57.5%) | 16 (48.5%) | 373 (42.0%) | 0.09 |
| NSTEMI | 20 (42.6%) | 17 (51.5%) | 515 (58.0%) | 0.09 |
| CCS Class III or IV during hospitalization | 5 (10.6%) | 1 (3.0%) | 127 (14.3%) | 0.14 |
| Cardiogenic shock | 6 (12.8%) | 6 (18.2%) | 87 (9.8%) | 0.25 |
| Ejection fraction, % | 50.3 ± 14.9 | 52.8 ± 11.0 | 48.3 ± 14.7 | 0.25 |
| Laboratory values | ||||
| Hemoglobin A 1c | 7.9 ± 3.0 | 6.5 ± 1.5 | 7.2 ± 2.1 | 0.09 |
| Leukocytosis (white blood cells >10,000/μL) | 21 (44.7%) | 17 (51.5%) | 393 (44.3%) | 0.59 |
| Hematocrit % | 41.8 ± 4.1 | 43.2 ± 5.1 | 39.4 ± 5.9 | <0.0001 |
| White blood cell count (10,000/μL) | 10.1 ± 3.2 | 12.5 ± 6.8 | 10.2 ± 3.6 | 0.003 |
| Creatinine (mg/dL) | 0.79 ± 0.17 | 1.43 ± 3.15 | 1.20 ± 1.35 | 0.10 |
| Troponin I (ng/dL) | 1.85 ± 4.22 | 2.81 ± 4.80 | 2.30 ± 6.35 | 0.88 |
| Total cholesterol (mg/dL) | 202.5 ± 65.1 | 175.3 ± 48.2 | 173.2 ± 53.4 | 0.003 |
| Total cholesterol-HDL (mg/dL) | 164.2 ± 65.9 | 135.8 ± 46.1 | 132.4 ± 51.5 | 0.0007 |
| Triglyceride (mg/dL) | 234.5 ± 221.0 | 145.3 ± 67.4 | 156.0 ± 118.2 | 0.0004 |
| HDL (mg/dL) | 38.3 ± 12.2 | 39.5 ± 12.8 | 40.8 ± 13.5 | 0.46 |
| Triglyceride/HDL | 7.2 ± 8.3 | 4.4 ± 3.2 | 40.8 ± 13.5 | 0.004 |
| LDL (mg/dL) | 118.0 ± 52.1 | 106.3 ± 41.2 | 104.0 ± 54.6 | 0.27 |
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