PCI No Less Effective in High-BMI Patients Despite Greater Plaque Burden

In obese patients, vessels appear to adapt to atherosclerosis by remodeling outward, thereby preserving a larger lumen area after IVUS-guided stenting, according to an imaging substudy of the ADAPT-DES trial in the January 2015, issue of Circulation: Cardiovascular Interventions. As a result, TLR rates are no higher than in lower-weight patients despite a greater plaque burden and more comorbidities in the high-BMI group. 

The main ADAPT-DES study correlated platelet reactivity with rates of stent thrombosis and other adverse events at 1 year in 8,575 registry patients who had been successfully treated with DES and were on dual antiplatelet therapy.

For the imaging analysis, investigators led by Akiko Maehara, MD, of Columbia University Medical Center (New York, NY), looked at 780 patients (average age about 64 years; 74.1% men) whose 916 culprit lesions were evaluated with grayscale and virtual histology (VH-) IVUS prior to PCI. In addition, IVUS was used to guide the procedure in most patients (94.3%) and to document the results in the rest.

The cohort was divided by BMI into tertiles:

 

• Low (median 23.8)
• Intermediate (median 27.4)
• High (median 31.9)

 

Patients with a high BMI were younger and more frequently had diabetes, hypertension, hyperlipidemia, and lower LVEF.

The normalized volume of plaque plus media was greater in the high-BMI group than the low-BMI group (8.9 vs 7.6 mm³/mm; adjusted P = .01), although a larger external elastic membrane (EEM) volume helped to preserve lumen volume in the high-BMI group. Similarly, at the minimal lumen area (MLA) site, the high-BMI group had a greater plaque burden and a larger EEM area but a similar MLA compared with the lower-BMI groups.

High BMI Linked to Positive Remodeling

Compared with low BMI, high BMI was more often associated with plaque rupture and showed greater normalized volumes of VH-IVUS necrotic core and dense calcium.

As in the overall cohort, among patients propensity-score matched for age, sex, diabetes, and renal insufficiency, high BMI was linked to a greater normalized EEM volume and necrotic core volume, and more plaque rupture compared with low BMI (all P < .05). The association of high BMI with greater normalized EEM and plaque plus media volume held true regardless of whether patients had ACS, while its link to more plaque rupture was only seen in the ACS subgroup.

After PCI, the high-BMI group—which received larger stents—had larger minimal stent area and MLA compared with the lower tertiles (P = .003 and P = .005, respectively).

There were no differences in rates of acute malapposition or frequency of tissue protrusion or proximal or distal edge dissections based on BMI.

Immediate PCI outcomes and 1-year adverse cardiac events including death, MI, and stent thrombosis were similar across BMI tertiles. A trend was seen toward less clinically driven TLR in the high- vs the low-BMI groups for both the propensity-matched cohort (1.8% vs 5.8%; P = .051) and the overall study group (2.0% vs 5.0%; P = .053).

Mechanism for the Obesity Paradox?

According to the Dr. Maehara and colleagues, positive remodeling in patients with a high BMI, as indicated by a larger EEM area and volume, shows a “greater compensatory response to plaque accumulation that preserved the lumen area and volume.”

They say the findings suggest a plausible explanation for the so-called obesity paradox, in which higher-weight patients have better outcomes than their normal-weight counterparts. “Even in the setting of a greater plaque burden, a larger EEM in the high-BMI group allows for the use of larger stents and larger balloons to achieve greater stent expansion and a larger minimum stent area,” especially under IVUS guidance, they explain.

Previous studies have shown stent area to be the strongest determinant of 1-year TLR because greater stent expansion provides more room for intimal hyperplasia, the investigators observe. Thus, patients with a high BMI—who exhibit traits associated with vulnerable plaque as well as comorbidities like diabetes, hypertension, and hyperlipidemia—did not have worse outcomes, possibly due to stent expansion.

In an email with TCTMD, Carl J. Lavie, MD, of Ochsner Medical Center (New Orleans, LA), said the findings offer more support for the obesity paradox. He noted that the data are in line with a recent meta-analysis of 36 studies he coauthored showing that after revascularization (PCI or CABG) cardiovascular mortality was lowest among patients with a high BMI.

On the other hand, Dr. Maehara and colleagues add, high BMI predicts plaque rupture, and as such, they argue for further research “to clarify how obesity contributes to the plaque vulnerability.”

The authors acknowledge that due to a paucity of hard events, the current study was underpowered to determine the effect of BMI on stent thrombosis and mortality. In addition, they say, it is unclear whether vascular remodeling is related to large body size per se or is mediated by other mechanisms in obese patients.

Note: Dr. Maehara and several coauthors are faculty members of the Cardiovascular Research Foundation, which owns and operates TCTMD.

 

 

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Source:
Kang S-J, Mintz GS, Witzenbichler B, et al. Effect of obesity on coronary atherosclerosis and outcomes of percutaneous coronary intervention: grayscale and virtual histology intravascular ultrasound substudy of Assessment of Dual Antiplatelet Therapy With Drug-Eluting Stents. Circ Cardiovasc Interv. 2014;Epub ahead of print.

 

Related Stories:

• Obesity Paradox Revisited: Lower BMI Linked to Higher Death, CV Events After PCI
• Study Finds No ‘Obesity Paradox’ in DES-Treated Patients
• Higher BMI Linked to Lower Mortality, More Metabolic Disorders After PCI