Download How A Coronary Stenosis Progresses

How A Coronary Stenosis Progresses
San Francisco, CA - How a coronary stenosis that is only moderate in angiographic severity progresses,
especially if it is bypassed with a vein or arterial graft, may differ according to the involved side of the heart [1].
Stenoses in coronaries serving the left side of the heart that are moderate in severity—that is, those taking up
40% to 69% of luminal diameter (grade 1)—appear to worsen more aggressively than those on the right side,
which may not progress much at all unless they are bypassed.
The insights came from a cohort of patients with coronary disease who were mostly asymptomatic on
optimal medical therapy and who nonetheless underwent serial coronary angiography and clinical
follow-up for up to a decade as part of an ongoing clinical trial—an opportunity to track the effects of
CABG on the natural history of native-vessel stenoses.
So I think FFR to guide the actual revascularization of these lesions in the future will be the way to go.
If they turn out to be true with further study, they could potentially help guide decisions on the extent
of revascularization during bypass surgery, said Dr Phillip A Hayward(University of Melbourne,
Parkville, Australia) here at the American Association of Thoracic Surgery 2012 Annual Meeting.
He said the analysis was based on 405 patients followed for a mean of 6.2 years, in whom 386 grade
1 moderate coronary lesions were tracked along with 1183 severe lesions. Moderate lesions were
less likely to progress than severe lesions, "and the effect was widest in the right coronary artery."
Progression was defined as an increase by at least one stenosis-severity grade (0 to 4) or to
occlusion.
Rates (%) of angiographic progression by right vs left heart circulation and moderate (40%-69% stenosis
severity) vs severe (>70% stenosis severity) bypassed lesions
Heart circulation Moderate (%) Severe (%) p
Overall
36.3
46.7
<0.001
Right
34.4
64.1
<0.001
Left
37.3
38.5
0.711
Moreover, bypass of a native-vessel lesion of any severity increased the risk of that lesion
progressing by fourfold overall. But the risk was 50% higher if the native coronary served the right
side of the heart, such as the right coronary artery. The risk was lower, though still increased, on the
left side of the heart, such as in the left anterior descending or left circumflex coronary artery.
So disease progression seems to "behave differently," depending on the side of the heart served by
the vessel, according to Hayward.
It's been suggested that grafting alters the natural history of atheroma by changing patterns of flow, and
this of course is entirely keeping with our data.
Focusing only on moderate lesions, he said, their progression rate on the left side is high if bypassed
but higher if not bypassed. "So our data would favor grafting that left-sided moderate lesion."
But on the right side, a moderate lesion has a low rate of progression if bypass is not performed,
Hayward said; its progression rate goes up threefold, however, if it is bypassed. "On the right side, if
you leave that lesion undisturbed, there's a very low chance of progression, and therefore our data
would favor leaving such a lesion [unbypassed]."
Rates (%) of angiographic stenosis progression and regression by whether bypassed or not bypassed, for
all lesions and for moderate lesions
Heart
circulation
Bypassed (all
lesions)
Nonbypassed (all
lesions)
Bypassed
(moderate lesions)
Nonbypassed
(moderate lesions)
Progression
43.4
10.5a
37.2
31.7
Regression
15.2
2.6a
10.5
14.3
Progression
62.1
10.1a
40.2
13.8b
Regression
11.4
2.1a
7.8
10.3
Progression
35.8
10.7a
35.7
47.1
Regression
16.7
2.9a
11.8
17.6
Overall
Right
Left
a. p<0.001 vs bypassed (all lesions)
b. p=0.008 vs bypassed (moderate lesions) and p<0.01 vs left circulation progression for nonbypassed
(moderate lesions)
Interestingly, Hayward said, bypassing a less-than-moderate lesion leads to greater progression on
the right side than on the left side. For example, if lesion severity is overestimated at the procedure,
"and what you thought was a moderate stenosis, on review by another angiographer was really less
than a 40% stenosis, if you bypass it on the right side, you get a dramatic 18-fold increase in
progression. If you bypass it on the left side, you still get more progression but much less."
Effect of bypass on coronary lesions of 0% to 39% (not significant stenosis) by right vs left circulation
Location of progression
Bypassed lesions (%) Nonbypassed lesions (%)
Overall coronary circulation 35.7
6.6
Right circulation
78.9
4.6
Left circulation progression
25.8
7.7
p<0.001 for all differences between bypassed and nonbypassed and for progression in bypassed right vs
left circulation
As the assigned discussant for Hayward's presentation, Dr Joseph F Sabik (Cleveland Clinic, OH)
said the guidance from the analysis, that left-sided moderate lesions might be more suitable for
bypassing than moderate right-sided lesions, would be strengthened by assessing the lesions'
hemodynamic impact. He pointed out that such assessments for guiding stent placement in
the Fractional Flow Reserve versus Angiography for Guiding PCI in Patients with Multivessel
Coronary Artery Disease (FAME) trial led to significant reductions in death, MI, CABG, or repeat PCI.
"In other words, stenting moderate or non-ischemia-producing coronary artery stenoses resulted in
worse clinical outcomes. Might this also be true for routinely grafting coronary arteries with only
moderate or non-ischemia-producing lesions?"
Hayward replied that yes, he thinks that FAME and also the DEFER trial, evaluating fractional flow
reserve (FFR) for selecting moderate lesions for stenting, "in some ways can be extrapolated to this
study." In FAME, among patients with non-flow-limiting lesions, those who received stents fared
worse than those who did not get stents.
"I think most surgeons would recognize that if you put a stent in a vessel that is not actually flowlimiting, that's going to impact your long-term outcome, because it represents a lifetime risk. [But]
we've probably felt that if we put a bypass graft to a vessel and it doesn't match the flow-limiting
[characteristics], well, the worse that can happen is the graft will fail, and you haven't done any harm.
I think what's interesting in our data is that that may not be true, that the findings of FAME and
DEFER might relate to surgery as well: putting a bypass through a vessel that doesn't need it might
be a bad thing," Hayward said. "So I think FFR to guide the actual revascularization of these lesions
in the future will be the way to go."
Lesions might appear to progress more in grafted vessels than nongrafted vessels because
"surgeons might just be good at predicting which lesions are going to progress," Hayward said. But
"it's been suggested that grafting alters the natural history of atheroma by changing patterns of flow,
and this of course is entirely keeping with our data."
As to why moderate lesions would progress differently on the left and right sides, "it may be that the
pathophysiology is different" on each side. "We know [from pathologic and imaging studies] that the
burden of coronary disease is higher in the overall population in left-sided compared with right-sided
vessels," Hayward said. "And it's been postulated that left-sided vessels have more shear stresses
and a different flow pattern compared with the right coronary artery." The difference could be related
to the more forceful myocardial mechanics and hemodynamics on the left side.
"So I guess it's possible that in modern secondary prevention, particularly with statins and their
effects on lipids and inflammation, those two drivers of atherosclerosis may exert different effects in
the right and left coronaries." But statins, he noted, would not alter shear stresses, "which are driven
by the left ventricle. That is the only reason I can think of why over 20 years of advances in medical
therapy might have left us with these very stable right coronary lesions."
Neither Hayward nor Sabik had disclosures.
Source
1.
Hayward PA, Zhu YY, Hare DL, Buxton BF. Should all moderate coronary lesions be grafted
during primary coronary bypass surgery? An analysis of disease progression during angiographic
surveillance in a trial of conduits. American Association of Thoracic Surgery 2012 Annual Meeting;
May 1, 2012; San Francisco, CA. Abstract 32.
Related links
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What's "normal?" Little consensus on CAD extent, severity among Ontario angiographers
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