Chronic stable angina PCI and CABG versus medical therapy


 * Associate Editor(s)-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S.

Overview
The Mass and Mass-II trials directly compared the effect of medical therapy, CABG and PCI for the management of chronic stable angina. However, there are a few reservations to the application of results from these studies as they did not include the current optimal strategies of therapy.

Limitations
There are some reservations to the application of results from older randomized trials such as Mass and Mass II trials to the current clinical practice as they assessed patients prior to the era of current optimal medical regimen, aggressive lipid-lowering therapy, drug-eluting stent and lifestyle intervention.

Clinical Trial Data
===The Medicine, Angioplasty or Surgery Study (MASS) ===

Study Population
214 patients with chronic stable angina, normal ventricular function and a proximal stenosis of the left anterior descending coronary artery greater than 80% were randomized to undergo mammary bypass surgery (n=70), balloon angioplasty (n=72) or medical therapy alone (n=72).

Results: Primary end-point
The composite primary endpoint of all cause mortality, non-fatal MI or refractory angina requiring revascularization, during a mean follow-up of 3-years was significantly different among the PCI and CABG groups (P=0.0002) and among the CABG and medical therapy groups (P=0.006) and no significant difference observed between the PCI and medical therapy group (P=0.28): 3% in the CABG group, 24% in the PCI group and 17% in the medical therapy group. However, there was no difference in mortality or infarction rates among the groups.

Results: Secondary end-point

 * No patient allocated to bypass surgery needed revascularization, compared with eight and seven patients assigned, respectively, to PCI and medical therapy (P=0.019).


 * Both revascularization techniques resulted in greater symptomatic relief and a lower incidence of ischemia on the treadmill test; however, all three strategies eventually resulted in the abolition of limiting angina.

Conclusion
The study concluded that for patients with a single severe proximal LAD stenosis, a more aggressive therapeutic approach with initial bypass surgery was associated with a lower incidence of medium-term adverse events than with PCI or medical therapy. However, all the three strategies resulted in a similar incidence of death and infarction during an average follow-up period of 3 years.

===MASS: 5-year Follow-up ===

The primary endpoint defined as the occurrence of acute MI, death or presence of refractory angina requiring revascularization, during a 5-year follow-up was significantly lower with CABG group than with PCI or medical therapy (6 patients versus 29 patients and 17 patients respectively; P=0.001). However, all the three treatment regimens yielded a similar incidence of cardiac-related death (P=0.622). Thus, the study concluded that CABG for single-vessel disease was associated with a lower incidence of medium-term and long-term events as well as fewer anginal symptoms than with PCI or medical therapy.

===The Medicine, Angioplasty or Surgery Study (MASS-II) ===

Study Population
611 patients with multi-vessel disease (58% had triple-vessel disease and 92% had LAD disease), preserved ventricular function and chronic stable angina with CCS class II or III were randomized to undergo CABG (n=203), PCI (n=205) or medical therapy alone (n=203).

Results: Primary end-point
The incidence of composite primary endpoint of all cause mortality, Q wave MI or refractory angina requiring revascularization, during a 1-year follow-up was significantly lower with PCI than with medical therapy or CABG group (76% versus 88% and 93% respectively). However, the 1-year mortality was significantly lower with the medical therapy group than with PCI or CABG (1.5% versus 4.5% and 4.0% respectively).

Results: Secondary end-point

 * After one-year follow-up, 8.3% of medically treated patients and 13.3% of PCI patients underwent additional interventions, compared to only 0.5% of CABG patients.


 * At one-year follow-up, 88% of the patients in the CABG group, 79% in the PCI group, and 46% in the medically treated group were free of angina (P<0.0001).

Conclusion
The study concluded that medical therapy for multi-vessel CAD was associated with a lower incidence of short-term events and a reduced need for additional revascularization, compared with PCI. In addition, CABG was shown to be superior to medical therapy for eliminating anginal symptoms. However, all the three therapeutic regimens yielded relatively low rates of cardiac-related deaths.

===MASS-II: 5-year Follow-up ===


 * The incidence of composite primary endpoint from all cause of mortality, Q wave MI or presence of refractory angina requiring revascularization, during a 5-year follow-up was found to be significantly lower with CABG group than with PCI or medical therapy (21.2% versus 32.7% and 36% respectively; P=0.0026). However, no statistical difference was observed in the overall mortality among the three groups.


 * The pairwise treatment comparisons of the primary end points showed no difference between PCI and medical therapy group (RR 0.93; 95% CI, 0.67 to 1.30) and a significant protective effect of CABG compared with medical therapy (RR, 0.53; 95% CI, 0.36 to 0.77).


 * In addition, a significant number of patients who received medical therapy and PCI underwent repeat revascularization procedures compared to the CABG group (9.4% versus 11.2% and 3.9% respectively; P=0.0026). Moreover, 15.3%, 11.2%, and 8.3% of patients experienced non-fatal myocardial infarction in the medical therapy, PCI, and CABG groups, respectively (P<0.001).


 * No significant difference in survival was noted among the three groups (88% to 92%).

===MASS-II: 10-year Follow-up ===

The incidence of primary endpoint, during a 10-year follow-up was significantly higher with CABG group than with PCI or medical therapy (73% versus 55% versus 49% respectively). Relative to the composite end point, Cox regression analysis showed a higher incidence of primary events in medical therapy than in CABG (HR 2.35; 95% CI, 1.78 to 3.11) and in PCI than in CABG (HR 1.85; 95% CI, 1.39 to 2.47).

The 10-year rates of myocardial infarction was significantly higher with medical therapy than with PCI or CABG group (20.7% versus 13.3% and 10.3%; P<0.010).

The 10-year rates of additional revascularizations was significantly higher with PCI than with medical therapy or CABG group (41.9% versus 39.4% and 7.4%; P<0.010).

No significant difference in survival among the three groups (69% to 75%).

Thus, the study concluded that in comparison to CABG, medical therapy and PCI were associated with a significantly higher incidence of subsequent myocardial infarction, a higher rate of additional revascularization, a higher incidence of cardiac death, and consequently a 2.29-fold increased risk of combined events with medical therapy and a 1.46-fold increased risk with CABG. Additionally, CABG was better than medical therapy at eliminating anginal symptoms.