Burlington, VT - New research finds that cardiac fitness levels in men and women recovering from surgical and nonsurgical interventions are significantly lower than previously believed [1]. Fitness in women entering cardiac rehab programs is particularly low, the authors say.

"I don't think [cardiologists] realize how extremely unfit the women are at this time frame, roughly one month after a cardiac event," lead author on the study, Dr Philip A Ades (University of Vermont College of Medicine, Burlington), told heartwire. "They not only were in the range at which we often send people for transplantation—which is already surprising—they were at a level where easily half of the women at this point in time would not have been able to do most of their household activities, things like light housework or cooking."

Ades and colleagues, whose study was published online June 5, 2006 in Circulation, say their findings should be a wake-up call to physicians who may be overestimating patients' fitness capacity and should reaffirm the importance of cardiac-rehabilitation programs.

"The message to cardiologists and cardiac surgeons is, if you think you're done when you put in the stents or do the bypass surgery, you're only halfway there," Ades stated. "When cardiologists and cardiac surgeons realize, 'Hey, I thought I fixed this person and look how unfit they are,' they can emphasize the need for proper rehab to complete their patient's recovery."

Treadmill tests are usually performed when patients are first admitted into cardiac-rehabilitation programs, typically within four to six weeks after undergoing CABG or PCI. But as the authors note, VO₂ max is rarely specifically measured but instead estimated from maximal exercise capacity in metabolic equivalents (METS), often without being adjusted for age or sex. There are also no established norms for patients entering rehab programs—instead, normal ranges and goals are derived from chronic heart disease patients and don't take into account deconditioning after cardiac interventions.

To better understand aerobic fitness in this group, Ades et al performed exercise stress testing with expired gas analysis in 2081 men and 815 women entering cardiac rehab programs at two hospitals between 1996 and 2004. All of the study participants had previously been hospitalized for MI or chronic angina and had undergone CABG or PCI or received medical therapy.

The authors report that peak VO₂ was significantly higher in men than in women; peak VO₂ decreased with age and, in men, at a faster rate of decline; and lower VO₂ was associated with CABG surgery, angina during stress testing, hypertension, and longer hospitalizations. Strikingly, peak VO₂ levels measured directly using expired gas analysis were considerably lower than the levels achieved using standard equations to convert METS to peak VO₂. "When we used the standard equations to convert METS to peak VO₂, it overestimated fitness by 30%," Ades commented. "So the vast majority of rehab programs that use these calculations really think these folks are fitter than they are."

In a subset of 504 patients who underwent repeat testing after 36 cardiac rehab sessions, aerobic capacity improved by an average of 17%, with larger gains in men than in women; gains for both men and women were greater among those who took cardiac rehabilitation, as compared with people who did not.

"Our results document that peak VO₂ values were far lower than age-matched norms for healthy individuals and lower than previously published values in cardiac-rehabilitation patients," the authors concluded. "These findings imply very high levels of physical disability in contemporary populations of cardiac patients, who should benefit significantly from participation in cardiac rehabilitation exercise training protocols."

To aid clinicians in determining appropriate baseline fitness levels and individualized rehabilitation plans, Ades et al's paper provides tables indicating age- and gender-based estimates of "normal" for patients entering cardiac-rehabilitation programs, something Ades describes as a missing link.

"I've been doing these stress tests for 20 years, and it has always amazed me that when I have a patient entering cardiac rehab I don't know where they stand compared with other people their age and diagnosis," he said. "Here I'm supposed to be the expert, and I can't even tell a patient if they are average, above average, or below average for their age for someone a month after bypass surgery. And that's always surprised me, because this is not a rare event."

The paper also provides a revised calculation to more accurately estimate peak VO₂ from METS.

According to Ades, knowing the accurate baseline fitness levels of patients entering a cardiac-rehabilitation program is important on several levels. For one, knowing the starting point can help patients and physicians to set reasonable goals. "If someone is 20% below average, you're not going to tell him that three months from now, he's going to be 20% above average," Ades said.

And while rehabilitation involves more than improving cardiac performance and needs to be tailored to individuals, knowing accurate baseline peak VO₂ values is important, Ades said.

"There are other things we do in cardiac rehab besides improve peak VO₂, but we know from other studies that peak VO₂ is the single best indicator of whether a patient is disabled—it's a very powerful predictor of their ability to manage at home."