Heart prevention

Examining the paradox of obesity in STEMI patients

Dr. Ian J. Neeland
Dr. Ian J. Neeland

By Ian J. Neeland, M.D., FAHA
Assistant Professor of Internal Medicine

Approximately every 42 seconds, someone in the U.S. has a myocardial infarction, or “heart attack,” according to the American Heart Association. The most serious type, ST-elevation myocardial infarction (STEMI), accounts for about one-third of all heart attacks and can be fatal if not treated promptly.

Both age and weight are linked to increased risk for STEMI. In many health conditions, however, we observe an obesity paradox in which patients with normal body weight have a worse prognosis than overweight or obese patients. The reasons for this are not fully understood.

In this study, we set out to determine whether there was an obesity paradox among older adults with weight issues after STEMI and whether or not being extremely obese (body mass index ≥40 kg/m2) was associated with better prognosis after STEMI than being of normal weight.

We studied 19,499 patients with STEMI from 503 hospital sites in the U.S. between 2007 and 2011 in the National Cardiovascular Data Registry with linkage to Medicare. Patients were categorized by weight class into normal weight; overweight; and mild, moderate, or extremely obese. We then observed rates of death, days alive and out of the hospital, and readmission for myocardial infarction, heart failure, or stroke over the three years following discharge after STEMI.

We found that the majority (70 percent) of older patients with STEMI were overweight or obese. We also confirmed an obesity paradox that mild obesity was linked to lower risk of death and living longer outside the hospital com­pared with normal-weight patients. However, patients with extreme obesity (3 percent) – most often female, black, and with lower income and education – did not show a paradox and remained at high risk for morbidity and mortality. 

Although further study is needed to discern the reasons behind these observations, the medical community should be aware that the rapidly growing population of patients with extreme obesity is at notably increased risk for poor outcomes after STEMI.

"Both age and weight are linked to increased risk for STEMI. In many health conditions, however, we observe an obesity paradox in which patients with normal body weight have a worse progno­sis than overweight or obese patients."

Understanding ‘cholesterol efflux’ to miti­gate heart attack, stroke

Dr. Anand Rohatgi
Dr. Anand Rohatgi

By Anand Rohatgi, M.D.
Assistant Professor of Internal Medicine

As a preventive cardiologist, I work regularly with dietitians, exercise physiologists, and nurse practitioners to provide a comprehensive atherosclerotic risk assessment and an individually tailored lifestyle plan to reduce patients’ risk of heart attack and stroke. My research focuses on HDL, the “good” cholesterol, and how it functions.

There’s a significant amount of controversy about how to make HDL better, and simply rais­ing the HDL cholesterol numbers doesn’t seem to be enough. After conducting extensive research on the subject, our team at UT Southwestern found that the ability of a person’s HDL to remove cholesterol from macrophages strongly predicts a future risk of heart attack or stroke. 

Our primary research used data from the Dallas Heart Study, a multiethnic population-based study that comprised more than 6,000 Dallas County residents. Our study was the first to show that those with the lowest cholesterol removal ability, called “cholesterol efflux,” had the highest risk of suffering a cardiac event.

We published these findings in the New England Journal of Medicine in 2014, and they have supported our ongoing studies. We are now investigating whether a lab test can be devel­oped to measure cholesterol efflux and whether this information will help clinicians assess a patient’s risk and then offer a therapy that can improve that risk by improving cholesterol efflux.

We are also examining whether cholesterol efflux is inherited and, if so, what genes and proteins are responsible for determining a person’s cholesterol efflux capacity. With this knowledge, we hope to substantially reduce the risk of heart disease not just by lowering the bad cholesterol but also by amplifying the ability of good cholesterol to clean up arteries and prevent plaque build-up.

“After conducting extensive research on the subject, our team at UT Southwestern found that the ability of a person’s HDL to re­move cholesterol from macrophages strongly predicts a future risk of heart attack or stroke.”

Coronary calcium scores of zero: when seeing nothing is really seeing something

Dr. Amit Khera
Dr. Amit Khera

By Amit Khera, M.D.
Associate Professor of Internal Medicine
Director, Preventive Cardiology Program

Coronary artery calcium (CAC) scanning is fast becoming one of the most com­monly used tests for refining cardiovas­cular (CV) risk assessment. A wealth of data, including from the Dallas Heart Study, shows that higher CAC scores correlate with a higher risk of CV events, and that CAC results are much more powerful than several other risk markers, including C-reactive protein.

However, an intriguing emerging concept with CAC is the power of zero. Rather than trying to detect occult CAC in lower-risk individuals, here, the objective is to offer some reassurance and “de-risk” individuals who have a score of zero.

I served as a moderator for a recent Great Debate at the AHA Session titled “The High-Risk Patient with a CAC Score of Zero.” Khurram Nasir, M.D., M.P.H., who has written extensively in this area, presented his well-known study involving the MESA cohort, comprising individuals who had a 10-year risk of atherosclerotic events between 5 to 20 percent, where statins can be considered. He demonstrated that about half of these individuals had a CAC score of zero and thus might not need treatment.

This paradigm, when applied to the adult U.S. population, could result in millions of patients having a less compelling need for a statin than is currently recommended.

On the other hand, Jennifer Robinson, M.D., M.P.H., who is Co-Chair of the 2013 ACC/AHA Cholesterol Guidelines, offered an equally compelling argument based on the same MESA data, which she said show that a CAC score of zero in middle-age to older adults essentially cuts one’s estimated risk in half – so a risk of 8 percent by current risk calculators would be a risk of 4 percent when the CAC score is zero. Although this represents a significantly lower risk, and below our treatment threshold of 5 to 7.5 percent, the risk is not zero and the patient is not “bulletproof.”

There are additional considerations about such patients’ lifetime risk of CV events and whether they should be rescanned at some point in the future. A Dallas Heart Study-based abstract we presented at the AHA Sessions demonstrated that approximately 25 percent of individuals with a CAC score of zero would have a score greater than zero after seven years.

While the discussion was heated, the gen­eral consensus supported the idea that a CAC of zero is a valuable decision aid and assists in the patient-clinician discussion.

In the era of personalized medicine, such data can help individualize decisions and empower patients with a more accurate assessment when weighing their own goals, beliefs, and concerns. Ultimately, a patient’s CAC score represents one of the few times in medicine when seeing nothing is really seeing something. 

“This paradigm, when applied to the adult U.S. population, could result in millions of patients who have a less compelling need for a statin that is currently recommended.”

 

Physician Referral Information

UT Southwestern welcomes referrals from providers seeking optimal care for heart patients. Physicians and offices can refer a patient with one easy call to the heart intake coordinator, a registered nurse who is available 24 hours a day, seven days a week. Same-day access is available for patients experiencing chest pain and chest discomfort. To refer a patient to any UT Southwestern clinic or for general inquiries, call Patient and Physician Referral Services at 214-645-8300.

Clinical Heart Center Patient Referrals

Phone: 855-240-0816
Fax: 214-645-7269

Questions or Comments

If you have any questions or would like more information about the Clinical Heart Center or the recent AHA Scientific Sessions, contact Dr. Mark Drazner, Clinical Chief of Cardiology, at mark.drazner@utsouthwestern.edu.

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