the calcium is circumferential, are considered to be hard to dilate in regards to balloon angioplasty. complex lesions are one of the key predictors of poor outcome in percutaneous coronary intervention (pci), hence calcium lesion modification is needed before implantations of stents. the aim is to create cracks in the calcium within the vessel wall in order to increase the likelihood of successful expansion of the stenosis and delivery of the final stent. this is traditionally achieved by balloon angioplasty or debulking strategies including rotational, orbital and laser atherectomy. however, coronary intravascular lithotripsy using acoustic shockwaves is a novel approach for treating superficial and deep calcium in the vessel wall. usage percutaneous coronary angioplasty is one of the most common procedures performed during u.s. hospital stays; it accounted for 3.6% of all operating room procedures performed in 2011. between 2001 and 2011, however, its volume decreased by 28%, from 773,900 operating procedures performed in 2001 to 560,500 procedures in 2011. comparison to cabg most studies have found that cabg offers advantages in reducing death and myocardial infarction in people with multivessel blockages compared with pci. different modeling studies have come to opposing conclusions on the relative cost-effectiveness of pci and cabg in people with myocardial ischemia that does not improve with medical treatment. history main article: history of invasive and interventional cardiology coronary angioplasty, also known as percutaneous transluminal coronary angioplasty (ptca), because it is done through the skin and through the lumen of the artery, was first developed in 1977 by andreas gruentzig. the first procedure took place friday sept 16, 1977, at zurich, switzerland. adoption of the procedure accelerated subsequent to gruentzig's move to emory university in the united states. gruentzig's first fellow at emory was merril knudtson, who, by 1981, had already introduced it to calgary, alberta, canada. by the mid-1980s, many leading medical centers throughout the world were adopting the procedure as a treatment for coronary artery disease. angioplasty is sometimes referred to as "dottering", after interventional radiologist, dr charles theodore dotter, who, together with dr melvin p. judkins, first described angioplasty in 1964. as the range of procedures performed upon coronary artery lumens has widened, the name of the procedure has changed to percutaneous coronary intervention. research current concepts recognize that after three months the artery has adapted and healed and no longer needs the stent. complete revasculariztion of all stenosed coronary arteries after a stemi is more efficacious in terms of major adverse cardiac events and all-cause mortality, while being safer than culprit-vessel-only approach. controversy in 2007 the new england journal of medicine published the results of a trial called courage. the study compared stenting as used in pci to medical therapy alone in symptomatic stable coronary artery disease (cad). this showed there was no mortality advantage to stenting in stable cad, though there was earlier relief of symptoms which equalized by five years. after this trial there were widely publicized reports of individual doctors performing pci in patients who did not meet any traditional criteria. a 2014 meta-analysis showed there may be improved mortality with second generation drug-eluting stents, which were not available during the courage trial. medical societies have since issued guidelines as to when it is appropriate to perform percutaneous coronary intervention. in response the rate of inappropriate stenting was seen to have declined between 2009 and 2014. statistics published related to the trends in u.s. hospital procedures, showed a 28% decrease in the overall number of pcis performed in the period from 2001 to 2011, with the largest decrease notable from 2007. the 2017 orbita study has also caused much controversy, in that it found that following percutaneous coronary intervention there was no statistically significant difference in exercise time compared with medical therapy. the study authors believe that angina relief by pci is largely a placebo effect. others have noted the small sample size with insufficient power to detect outcome differences and the short 6 week duration of the trial. 85% of patients in the medical therapy arm elected to have pci at the end of the trial. the 2019 ischemia trial has confirmed that invasive procedures (pci or cabg) do not reduce death or heart attacks compared to medical therapy alone for stable angina. patients with angina experienced improved quality of life with pci compared to medical therapy.