Race and Gender Issues Influencing Atrial Fibrillation Management — News from Heart Rhythm 2010

June 1, 2010 5:04 AM CT

By Peggy Noonan and Mellanie True Hills

At Heart Rhythm 2010, the 31st Annual Scientific Sessions of the Heart Rhythm Society in Denver, Colorado, a session on “Demographic Factors Influencing Atrial Fibrillation Management and Outcomes” included two studies focused on the connection between race and atrial fibrillation risk and two studies focused on gender and atrial fibrillation. Here are highlights from those four sessions.

1.  African Americans Have Less Risk Than Caucasians of Atrial Fibrillation After Bypass Surgery

Topic:  “Incidence of Postoperative Atrial Fibrillation is Markedly Reduced in African Americans Compared to Whites”

Race is an important risk factor that doctors should consider when they project which patients may develop atrial fibrillation after heart surgery. This study at the Henry Ford Health System in Detroit, Michigan, analyzed records of 1,001 adult patients — 731 Caucasian, 270 African American — who did not have atrial fibrillation before they had heart bypass surgery.

First they measured high risk factors, including age, congestive heart failure, heart disease, high blood pressure, and diabetes. Analysis showed African Americans had significantly more risk factors than Caucasians in the study, yet only 18% of African Americans developed post-bypass atrial fibrillation compared to 29% of Caucasians. In other words, Caucasians are about 60% more likely to develop post-bypass atrial fibrillation than African Americans.

While the researchers say further studies are needed to determine what underlying factors protect African Americans from developing post-op afib, until those studies are done, Marc K. Lahiri, MD, of the Henry Ford Health System, says “it seems viable for clinicians [doctors] to consider race as an important factor in the likelihood of patients developing postoperative AF.” He cautions that since Caucasians appear to be at increased risk of developing afib after heart surgery, doctors may want to consider the use of antiarrhythmic medications in conjunction with surgery.

See: African Americans Experience Lower Incidence of Post-Op AF Despite Risk Factors, Heart Rhythm Society, 5/13/10

2. Blacks Have Lower Risk of Atrial Fibrillation After Age 60 Than Whites Despite Higher Risk Factors

Topic:  “Racial Differences in Risk for Atrial Fibrillation Only Occurs in Older Patients”

Race and risk of atrial fibrillation was the subject of a related study, also presented by Marc K. Lahiri, MD, in which doctors at the Henry Ford Health System (HFHS) in Detroit reviewed clinical data on adults aged 18 or older who were seen at least twice at HFHS between January 1, 2007, and December 31, 2008.

Of the 156,471 (63.6%) white and 89,588 (36.4%) black patients in the study, atrial fibrillation was diagnosed in 5,273 (3.4%) whites and 1,997 (2.2%) blacks.

Black patients had a higher prevalence of atrial fibrillation risk factors:

  • high blood pressure — 42.5% of blacks had hypertension compared to 28.3% of whites
  • diabetes — 16.5% of blacks had diabetes compared to 10.9% of whites
  • congestive heart failure — 3.7% of blacks had CHF compared to 2.8% of whites
  • thyroid disease — 0.5% in blacks had thyroid disease compared to 0.3% in whites.

However, one atrial fibrillation risk factor was higher in whites — coronary artery disease — at 5.2% in whites compared to 3.6% in blacks. Coronary artery disease (CAD), also called atherosclerosis or hardening of the arteries, is caused by cholesterol and fat plaque build-up inside artery walls which narrows blood flow to the heart and can cause heart attack.

Age played a role, too. There was no difference in prevalence of atrial fibrillation in age-matched blacks and whites in the 18-49 age group or 50-59 age group, but starting at age 60, rates of atrial fibrillation were lower in blacks than in whites even though most other risk factors were higher in blacks:

  • age 60-69 — 3.4% of blacks had afib compared to 4.1% of whites
  • age 70-79 — 6.0% of blacks had afib compared to 8.5% of whites
  • age 80 and older — 10.8% of blacks had afib compared to 13.2% of whites

The study showed that blacks and whites had similar rates of afib at younger ages, but that blacks had lower rates at older ages even though they had higher risk factors. It was mentioned that these disparities could possibly be associated with age-related differences in atrial fibrillation mechanisms, with atrial remodeling and areas of fibrosis being responsible for afib in those who are older, which appears to be more prevalent in whites, whereas ectopic foci (discrete sites that trigger atrial fibrillation) may be linked to afib in those who are younger, which appears similar in both.

Some potential differences were also raised in the subsequent Q&A session, such as whether African-Americans with afib potentially die younger, thus leading to some of this disparity, and whether there could be structural differences in the heart due to race that could make a difference since some data has shown that the left atrium tends to be smaller in African-Americans.

3.  Women with Atrial Fibrillation May Need More Aggressive Anticoagulation Than Men to Avoid Stroke

Topic:  “Is Risk of Ischemic Stroke in Atrial Fibrillation Gender Specific due to Differences in Anticoagulation?”

Women with atrial fibrillation are at higher risk of stroke than men with afib, but the reason for this difference is not clear.

Renee M. Sullivan, MD, of the University of Iowa, presented a study that explored the possibility that “Time in the Therapeutic Range” (TTR) might be responsible for these differences. TTR indicates how much of the time a person’s INR (International Normalized Ratio) is between 2.0 and 3.0, the therapeutic range for anticoagulants. This is an indirect measure of how well anticoagulation is working.

The study used data from the multicenter AFFIRM (Atrial Fibrillation Follow-up Investigation of Rhythm Management) Trial in which atrial fibrillation patients were randomly assigned to a treatment strategy using either rate control or rhythm control medicines. Anticoagulation treatment was recommended, too, but it was not required for the study and it was left to physicians to decide whether or not blood thinner drugs like Coumadin (warfarin) should be added to a patient’s treatment plan.

The researchers used the AFFIRM Trial’s data on 2,337 men and 1,499 women and assessed their time in treatment range (using the Rosendaal method INRPRO) and INRs at the time of their ischemic (clot-caused) stroke or death.

Their analysis showed that:

  • Women had more ischemic strokes, those caused by clots, than men.
  • Women spent more time outside of therapeutic range than men. On average, women were outside of therapeutic range 40% of the time compared to men’s 37%.
  • Women also spent more time below the therapeutic range — where the blood is “thicker” and thus more vulnerable to clots — at 29% compared to men’s 26%.
  • Both women and men were generally in therapeutic range at the time of their ischemic stroke or death.

What do these findings mean to women with atrial fibrillation? “To reduce risk of stroke, women with atrial fibrillation may benefit from novel anticoagulants [the coming Coumadin-replacement drugs],” the researchers said, “or require more aggressive anticoagulation compared to men.”

For more about:

4. Women with Atrial Fibrillation Are Referred Less Often to AF Centers and Are Less Likely to Receive Aggressive Treatments

Topic:  “Gender Differences in the Clinical History and Treatment of Patients Referred to an Atrial Fibrillation Center”

Another study, presented by Pamela K. Mason, MD, of the University of Virginia Health System, explored gender differences in atrial fibrillation. Although men have atrial fibrillation more than women do, women live longer, so the total number of atrial fibrillation cases is actually the same in women and men.

Researchers analyzed data on 1,664 consecutive patients who were seen at the University of Virginia AF Center between 2004 and 2008 to find out how gender affects atrial fibrillation. They knew from the RACE study that women on rhythm control treatment had more adverse events than those on rate control.

They report finding these notable gender differences:

  • Women were referred to the AF Center less often, almost half as often as men — 34.3% for women compared to 65.7% men
  • Women were older when they were first sent to the AF Center compared to men’s ages at their first visits. On average, women were 68 when referred while men were 62.4.
  • Women were diagnosed with atrial fibrillation at older ages than men, with women averaging 62.7 whereas men averaged 57.3
  • Women were more likely than men to be diagnosed with paroxysmal atrial fibrillation (68.0% women, 58.0% men) and had slightly more symptoms, including light-headedness or feeling faint (presyncope) and palpitations
  • Although there was no difference in women’s and men’s use of rhythm-control (antiarrhythmic) or clot-preventing (antithrombotic) medicines, women were more likely than men to be given rate-control medicines (70.2% of women, 63.1% of men)
  • The study found no gender difference in the prevalence of diabetes, high blood pressure or congestive heart failure, but women had less coronary artery disease (CAD) than men
  • Women were less likely than men to have undergone cardioversion before they were referred to the AF Center (23.2% women, 31.5% men)
  • Women were less likely than men to have an ablation procedure after they were referred to the AF Center (23.2% women, 40.4% men)

The researchers note that even when they took into account women’s older age, the differences between women and men with atrial fibrillation were “still significant.”

To learn more about Heart Rhythm 2010 and the research presented at the conference, see:

Peggy Noonan specializes in writing about health for consumers and medical professionals. She writes for leading national magazines and consumer publications as well as StopAfib.org.

Mellanie True Hills is founder and CEO of StopAfib.org and an atrial fibrillation survivor.