Cardiac shock-wave therapy in the treatment of refractive angina pectoris

As a result of the improvements in both pharmacologic and revascularization therapies life expectancy for patients with coronary artery disease (CAD) has greatly increased. This means that patients with more extensive CAD are now living longer, so many of them will develop myocardial ischemia and clinical angina that are not amenable to traditional revascularization therapy [1–4]. Patients with severe, symptomatic, chronic CAD have been described as having intractable angina, end-stage CAD or have been called ‘no option’ patients. However, despite being considered a therapy-resistant condition, refractory angina is a more appropriate term because a considerable number of new therapeutic methods are now available. The Canadian Cardiovascular Society (CCS) has recently defined refractory angina as a persistent (more than 3 months), painful condition, characterized by chest pain caused by coronary insufficiency in the presence of CAD, which cannot be controlled by a combination of medical therapy, angioplasty and coronary bypass surgery [5]. It is necessary to ensure that revascularization is unfeasible, medical therapy is optimal and that other causes of chest pain are excluded before establishing the diagnosis of refractory angina [5,6]. Currently, few data are available on the number of nonrevascularizable patients. Estimates have been obtained from both population surveys and catheterization laboratory registries. A Swedish survey in 1994–1995 demonstrated that approximately 10% of patients referred for coronary angiography because of stable angina were rejected for revascularization despite having severe symptoms [7]. In the late 1990s, a single tertiary referral center series reported that 12% of the patients referred for symptomatic CAD were not amenable to percutaneous coronary intervention or coronary artery bypass graft [8]. A more recent study conducted in Minnesota (MN, USA) found 6.7% of patients with coronary lesions >70% and no revascularization options despite optimal medical therapy [9]. In absolute numbers it would represent more than 100,000 new patients/year in the USA and 30,000–50,000 new patients/year in Europe who will probably fulfil the diagnosis of refractory angina [1,2,6]. The outcome of these patients continues to be controversial. The controlled trials with alternative therapies conducted in patients with refractory angina demonstrated (in their control arms) that annual mortality rates varied from 3 to 21%, whereas coronary event rates (including acute coronary syndromes and hospitalization for angina) varied from 11 to 69% [10–18]. In contrast to these trials, in a large series of 1066 patients with refractory angina followed for a median of 3.5 years only 126 patients died (11.8%), and only 58 of these deaths were from cardiovascular causes (5.4%) [19]. Data from 200 patients treated at our institution confirm this low rate (2% cardiac mortality per year) [20], and the recent study mentioned above also found a low mortality (15% at 3 years), although this was significantly higher than the mortality in patients completely revascularized (6.6% at 3 years) [9]. An increasing number of patients are being diagnosed with severe coronary artery disease not amenable to traditional revascularization. Most of them remain symptomatic despite optimal medical therapy, so the resulting qualiy of life is poor. Thus, there is a need for the development of novel therapies. Shock waves (SWs) have been used in medicine for 30 years, but the recent discovery of their potential angiogenic effect has led to their most promising application in cardiovascular medicine. Cardiac SW therapy delivered to ischemic myocardium has been demonstrated to reduce angina symptoms and to improve myocardial perfusion. And although there is a lack of large series and long-term follow-up, cardiac SW therapy is by now a safe, well-tolerated procedure with no significant side effects.