[Present trends and controversies in the use of beta-blockers in cardiovascular diseases]. / Beta-bloccanti e sistema cardiovascolare: attuali acquisizioni e controversie.

In this paper we summarize present trends and controversies in the use of beta-blockers in cardiovascular diseases. Beta-blockers are catecolamine competitive inhibitors and act through alpha and beta adrenergic receptors blockade. Different agents have a dose-dependent affinity for different beta adrenergic receptors (beta 1, beta 2, beta 3) which is less with higher doses. The most important therapeutic effects of beta-blockers are on cardiovascular system, where they act as negative chronotropic and inotropic agents, lowering cardiac work and improving oxygen demand /supply ratio. Clinical indications are numerous. For their anti-ischemic activity beta-blockers are used as anti-anginal drugs and in acute and previous myocardial infarction for preventing total and cardiovascular mortality. Combined use of beta-blockers and ACE inhibitors slows down heart failure progression and reduces cardiovascular mortality. Beta-blockers are useful in treating focal atrial tachycardia and supra ventricular paroxysmal tachycardia, by reducing sinus node automaticity and delay atrio-ventricular conduction; they also prevent sudden cardiac death and ventricular tachycardia associated with increased sympathetic activity. There is no indication in treating primary non-complicated hypertension with beta-blockers as first-line drugs. Different metabolic effects of selective and non-selective beta-blockers are actually debated. In conclusion, beta-blockers have indication in the treatment of many cardiovascular diseases. Further studies are needed for better understanding the differences in cardiac and peripheral beta-blockers effects depending on their selectivity.

Coronary slow-flow causing transient myocardial hypoperfusion in patients with cardiac syndrome X: long-term clinical and functional prognosis.

BACKGROUND: We investigated the possibility that transient coronary slow-flow as assessed during coronary angiography in patients with cardiac syndrome X may impair myocardial perfusion and the effects of this phenomenon on long-term prognosis. METHODS: From 50 consecutive patients with cardiac syndrome X, we prospectively recruited 16 who exhibited coronary slow-flow during angiography. The remaining 34 patients served as controls. The slow-flow phenomenon was invariably worsened by nitrates and reversed by papaverine. During slow-flow, a dose of 99m-Tc-Methoxy-isobutyl-isonitrile (MIBI) was injected in 12 patients and SPECT imaging performed 1 h later. The perfusion study was repeated after 2 days at rest and, in 9 patients, at peak exercise after 10+/-4 days. Patients were then regularly followed-up. RESULTS: All 12 patients had a significant MIBI defect in the regions served by the coronary artery that showed slow-flow just prior MIBI injection. After exercise, MIBI tomograms revealed a perfusion defect in 5 out of the 9 patients who underwent stress scanning. At 14+/-2 years follow-up, 1 patient with slow-flow had died and 4 developed significant coronary artery disease (CAD), while all patients of the control group were alive and none had developed significant CAD. CONCLUSIONS: These results show that the slow-flow phenomenon might be the cause of transient myocardial underperfusion in patients with angina and normal coronary arteries. Apparently, this phenomenon is associated with a worse cardiac prognosis. Therefore, patients with coronary slow-flow should be carefully followed-up.