Miami Heart Study Advances Preventive Cardiology as Coronary Plaque Detected in Nearly Half of Asymptomatic Participants

The first detailed report of the landmark Miami Heart Study, or MiHeart, launched in 2015 by teams at Miami Cardiac & Vascular Institute, part of Baptist Health, found “substantial prevalence of coronary plaque in asymptomatic individuals.”

Specifically, 49 percent of participants had coronary plaque, and 6 percent had stenosis (narrowing of arteries) of greater than 50 percent, the most serious risk factor for heart attack or stroke if untreated. 

Jonathan Fialkow, M.D., deputy medical director and chief of cardiology at Miami Cardiac & Vascular Institute.

“Ultimately, we want to prevent a preventable cause of death — and the most common preventable causes of death are heart attacks and strokes,” said Jonathan Fialkow, M.D., deputy medical director and chief of cardiology at Miami Cardiac & Vascular Institute and senior author of MiHeart, who manages the Institute’s teams that are following up with the study’s participants.

“Previously, we stratified who may have a heart attack or stroke with risk scores, which weighed risk factors such as hypertension (high blood pressure), diabetes, smoking and high cholesterol. And those risk scores were really not that predictive to an individual’s level. In fact, 15 to 20 percent of people who have heart attacks didn’t have identifiable main risk factors.”

Before the Institute launched MiHeart, the “burden of total coronary plaque, plaque subtypes, and high-risk plaque features was unknown in asymptomatic individuals,” according to the study’s authors in an article newly published by the Cardiovascular Imaging: A Journal of the American College of Cardiology.

Ricardo Cury, M.D., medical director of cardiac imaging at Miami Cardiac & Vascular Institute and Baptist Hospital.

“The MiHeart Study is the first US-based study utilizing Coronary CT Angiography to detect silent atherosclerosis in nearly half of participants, who are between the ages of 40 and 65, that likely had not been previously detected,” explains Ricardo Cury, M.D., medical director of cardiac imaging at the Institute and Baptist Hospital, who leads the imaging team for the Miami Heart Study.

“That’s a very important information and opens a new paradigm shift from risk stratification to early detection of disease, from primary to secondary prevention and from population health to precision medicine by tailoring the right treatments to the right patients based on actual presence, absence and severity of coronary artery disease. We know that heart disease remains the No. 1 killer in the US with more than 600,000 patients dying every year. So, the current prevention strategies are not been sufficiently effective.”

These findings of the ongoing study are being closely watched by medical professionals in the U.S. and globally because of the unique, diverse population being studied — more than 2,500 asymptomatic volunteers from South Florida, aged 40-65 at the beginning of MiHeart.

Khurram Nasir, M.D., chief of the Cardiovascular Prevention and Wellness Division of Houston Methodist Hospital, is MiHeart’s principal investigator. Dr. Nasir was part of Miami Cardiac & Vascular Institute when the study launched in 2015.

“As a community and as a health system, everyone you should be very proud of this accomplishment because there is no other study like it,” said Dr. Nasir. “Rather than waiting for others or being led, Baptist Health decided to lead.”

The study is also innovative on other fronts, including the focus on such a large group of individuals free of established cardiovascular disease or symptoms when recruited, and the use of coronary computed tomography angiography (CCTA) for baseline testing. A CCTA combines a CT scan and sophisticated computer analysis to provide detailed, 3D images of blood vessels and tissues. 

The baseline tests also include a coronary artery calcium (CAC) scoring, an exam that takes cross-sectional images of the vessels that supply blood to the heart muscle (coronary arteries) to look for the buildup of calcified plaque.. A CAC score of 100 to 300 represents moderate plaque deposits, but a score greater than 300 is associated with a relatively high risk of heart disease.

“The calcium score was developed and validated subsequent to the use of the prior risk scores and they provide the next step in moving from what we say is population data towards a more precise cardiovascular event predictor in an individual,” explains Dr. Fialkow. “Now, we want to figure out what the CTA’s actual value may be and what components of the plaque may have further risk stratification value. We believe this is going to be profoundly important as the next tool in precision risk stratification for the individual.

The goal with all the testing is to determine how much plaque and the precise plaque composition that develops in the arteries of this middled-aged group of adults (mean age 53 at start) who are asymptomatic. The ultimate goal: Understand how to more effectively intervene in the early stages of coronary artery disease and help prevent heart attacks and the full development of heart disease.

“I tell my patients that a zero-calcium score doesn’t mean your arteries are normal,” said Dr. Fialkow. “You can have soft plaque or inflammatory plaque that’s not calcified yet. But I can tell you that if you haven’t had calcium yet then your risk of a heart attack is relatively low over a period of a few years. Our ‘holy grail’ is not how to identify who may develop coronary artery disease (though this is profoundly important) but who has coronary disease that may lead to a non-fatal heart attack, non-fatal stroke or death by heart attack or stroke. The data from the MiHeart study and the correlation of the CTA findings with other measured markers and patient outcomes will help drive this knowledge

Another standout feature of MiHeart: The study includes a significant proportion of Hispanics (47 percent), and 49 percent of all participants are females. Both Hispanics and females are often underrepresented in cardiovascular studies.

Highlights of the MiHeart study results:

  • Overall, 58 percent of participants had CAC scores of 0; 28 percent had CAC between 0 and 100; and 13 percent had a CAC more than 100.
  • A total of 49 percent participants had plaque on the CCTA, including 16 percent among those with a CAC of 0.
  • Overall, 6 percent of participants had coronary stenosis of more than 50 percent, 1.8 percent had stenosis of more than 70 percent (3.7 percent among those with plaque), and 7 percent had at least one coronary plaque with more than one high-risk feature (13.8 percent among those with plaque).
  • Only 0.8 percent of participants with CAC of 0 had stenosis of more than 50 percent; 0.1 percent had stenosis of more than 70 percent, and 2.3 percent had plaque with high-risk features.

“The study’s impact will likely lead to a shifting of the paradigm from population health to more precision medicine because we know exactly of what is happening with the individual,” said Dr. Cury. “With the upgrade from CAC scoring to CCTA, you have a full coronary plaque assessment with not only detection of calcified plaque, but also non-calcified plaque, which are the plaques at higher risk of rupture and the ability to detect of coronary blockages/stenosis. It remains to be seen with longitudinal follow-up, but this additional information can better stratify patients who are at higher risk, particularly asymptomatic patients with diabetes, smoking or obesity and tailored the appropriate medical management based on the imaging findings.”

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