Little Consensus on CAD Extent, Severity Among Angiographers

Definitions vary for single-, double-, triple-vessel CAD

Shelley Wood

October 25, 2011

October 25, 2011 (Vancouver, British Columbia) — How is mild, single-, double-, or triple-vessel disease on an angiogram defined? Turns out that may depend on who is asked.

A recent survey of invasive and interventional cardiologists at cardiac centers in Ontario suggests there is very little agreement among physicians performing angiography as to how severity and extent of coronary artery disease are defined.

In recent years, variations in rates of revascularization, choice of revascularization procedure, and instances of "unnecessary stenting" have made headlines worldwide. In Ontario, work by the Cardiac Care Network, not yet published, has found striking differences in the ratio of PCI procedures to CABG, with implications for patient outcomes.

But as Dr Jon-David Schwalm (McMaster University, Hamilton, ON), who presented the new survey results here at the Canadian Cardiovascular Congress 2011, told heartwire, a fundamental first step to understanding appropriateness of revascularization procedures is reaching some agreement as to what represents significant disease. And while there are multiple documents and definitions of normal, mild, single-, double-, and triple-vessel disease, including an ACC/AHA Task Force on Clinical Data Standards [1], it's not clear that angiographers follow any specific guidance.

Dr. Jon-David Schwalm

"We wanted to look at, are there differences in what people call three-vessel disease, two-vessel disease, single, and mild disease?" Schwalm explained. "And is there a standard definition for these different classifications of coronary anatomy across centers?"

Schwalm and colleagues sent 188 thirteen-question surveys to the 18 cardiac centers in Ontario and got a response rate of 64% (120 surveys). Questions covered whether the responding physician was an invasive or interventional cardiologist and how they defined normal, mild, single-, double-, and triple-vessel disease, as well as additional questions on their personal hospital circumstance.

Shaking the (coronary) tree

Survey responses pointed to some striking differences in how physicians define single-, double-, and triple-vessel disease, with at least one-third of respondents to all three questions using much lower degrees of stenosis as a cut point.

Definition of single-vessel disease

Extent of disease 1 major epicardial vessel ≥70% 1 major epicardial vessel ≥50%
Responders (%) 65 35

Definition of double-vessel disease

Extent of disease 2 major epicardial vessels, each ≥70% 2 major epicardial vessels ≥50%
Responders (%) 58 37

Definition of triple-vessel disease

Extent of disease 3 major epicardial vessels, each ≥70% 3 major epicardial vessels ≥50%
Responders (%) 60 36

Moreover, 41% of respondents defined "mild" disease as < 30% stenosis, while 35% used a cutoff of < 50% stenosis. A full 69% of responders had very strict definitions of "normal": 0% stenosis and no luminal irregularities.

Different definitions would lead to different care

"We were quite surprised at what we found," Schwalm told heartwire. This degree of variability suggests that patient care would also vary widely, depending on the treating physician. "You could present at one center and have three 50% blockages in major epicardial vessels and could be referred on for surgery or PCI, whereas you could present with the same blockages at a different center, be labeled as 'mild,' and be sent home."

Schwalm stressed that he and his colleagues have not yet looked at how these different standards are affecting management, but they have some insights into who does what. For example, interventional and invasive cardiologists with less than 10 years of experience "tended to favor more stringent definitions of single-, double-, and triple-vessel disease," Schwalm said. By contrast, physicians with more than 10 years under their belts were more likely to use the cut points of 50% or greater.

And of note, more than two-thirds of survey responders said that they did not use or were not aware of any standardized definitions for reporting coronary anatomy at their hospitals.

"The simple message is that if we're going to look at variations [in use of revascularization procedures], we're starting on different playing fields from the get-go, and we're talking high-volume centers doing a lot of angiograms every year," Schwalm said. Understanding this variability in CAD definitions and diagnostics is an important first step before considering the larger question of whether people are getting appropriate care. "We've got to figure out what's going on here first before we can intervene to get people to follow evidence-based medicine," he said.

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