Review of the MASS II study

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MASS II is yet another study that shows the benefits of CABG compared to the limits of PCI as a viable long term strategy in stable patients with Coronary Artery Disease. This evidence adds to the ever growing body of literature promulgating the same in other risk groups (SYNTAX, SYNTAX-3 Analysis, BARI-2D, OAT trial, PCI vs. CABG – A Current Perspective, to name but a few).

Although a small single institution study, MASS II analyzed 10 year follow-up outcomes in patients randomizated not only to PCI and CABG, but also to Medical Therapy (MT).

Major Adverse Cardiac Events at 10-Year Follow-Up




P (Log-Rank)

Primary end points 42.4 59.1 33.0 <0.001
Overall mortality 24.1 31.0 25.1 0.089
Cardiac death 14.3 20.7 10.8 0.019
Additional intervention 41.9 39.4 7.4 0.001
AMI 13.3 20.7 10.3 0.010
CVA 5.4 6.9 8.4 0.550

AMI indicates acute MI; CVA, cerebrovascular accident.
Values are percentages.
  • The analysis demonstrated the superiority of CABG at 33% vs. both PCI (42.4%) and MT (59.1%) for the primary end point (mortality, Q-wave MI, and repeat revascularization , P=0.01).

Examination of the components showed that:

  • Overall Mortality was higher for MT (31.0%) although not statistically significant.
  • Cardiac death was lowest for CABG.
  • Subsequent revascularization was five times lower among patients with CABG (7.4%) and similar (about 40%) in patients with PCI and MT (P=0.01).
  • Individual clinical factors associated with increased mortality included age, presence of diabetes mellitus, and systemic hypertension. These same factors were also associated with an increased rate of cardiac death for MT as compared to CABG.

Although MT was associated with a significantly higher incidence of combined primary outcomes (cardiac death, MI and repeat revascularization), PCI was associated not only with increased repeat revascularization, a higher incidence of MI, and a 1.85-fold increased risk of combined events compared with CABG. No statistically significant difference (P=0.220) was found in overall mortality with these 3 treatment options. Additionally, CABG was better than MT at eliminating anginal symptoms.

The data from MASS II also showed that a routine strategy of MT for patients with stable multivessel disease was associated at 1o years with a significant reduction of event-free survival.


The 10-year results of MASS-II indicate that initial Optimal Medical Management, as propagated in the COURAGE trial, also seems to have been suggested in this study. An  MT strategy may be considered in stable patients in the early years; however, an interventional procedure may likely be necessary during follow-up.

In the long run, CABG improves outcomes the most for patients with multivessel disease and preserved heart function in comparison to MT and PCI, not only in mortality and MI, but especially in subsequent revascularization procedures.

Please let me know what you think,

Dr T


[i] Ten-Year Follow-Up Survival of the Medicine, Angioplasty, or Surgery Study (MASS II). Whady Hueb,et al. Circulation 2010;122;949-957

[ii] Is Optimal Medical Therapy “Optimal Therapy” for Multivessel Coronary Artery Disease? David O. Williams et al. Circulation. 2010;122:943-945.)

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