Dynamic coronary obstruction as a cause of angina pectoris: implications regarding therapy

Invasive testing for coronary artery disease: FFR, IVUS, OCT, NIRS

Coronary angiography is the gold standard for the diagnosis of coronary artery disease and guides revascularization strategies. The emergence of new diagnostic modalities has provided clinicians with adjunctive physiologic and image-based data to help formulate treatment strategies. Fractional flow reserve can predict whether percutaneous intervention will benefit a patient. Intravascular ultrasonography and optical coherence tomography are intracoronary imaging modalities that facilitate the anatomic visualization of the vessel lumen and characterize plaques. Near-infrared spectroscopy can characterize plaque composition and potentially provide valuable prognostic information. This article reviews the indications, basic technology, and supporting clinical studies for these modalities.

Role of coronary vasoconstriction in ischemic heart disease and search for novel therapeutic targets

Atherothrombosis has long been recognized as an important mechanism of cardiac events in ischemic heart disease, and large multicenter clinical studies have shown the benefit of antiplatelet agents, statins, beta-blockers and angiotensin converting enzyme inhibitors in preventing these events. However, more recent studies have been less successful at showing incremental gains in targeting these mechanisms, suggesting that the limits of this strategy have been exploited. Coronary vasoconstriction is another important mechanism in ischemic heart disease but has received little attention and yet is a potential therapeutic target. In the current review, the reasons why coronary vasconstriction has received insufficient consideration are explored. In particular, we need to change our approach from lumping heterogeneous clinical entities together to focusing on clinically-discrete homogeneous groups with a common mechanism and thus therapeutic target. The role of coronary vasoconstriction is examined in the various ischemic syndromes (variant angina, chronic stable angina, acute coronary syndromes and syndrome X) and the underlying mechanisms discussed. Finally, in order to advance studies in this field, an innovative research strategy is proposed, including: (1) selection of paradigmatic cases for the various ischemic syndromes; (2) candidate therapeutic targets; and (3) approaches in assessing the clinical efficacy of these potential therapies.

Vanidipinedilol: a vanilloid-based beta-adrenoceptor blocker displaying calcium entry blocking and vasorelaxant activities

Calcium channel and beta-adrenoceptor blockade have proved highly useful in antihypertensive therapy. Studies of the mechanisms of action of vanidipinedilol that combine these effects within a single molecule are described here. Intravenous injection of vanidipinedilol (0.1, 0.25, 0.5, 1.0, and 2.0 mg/kg) produced dose-dependent hypotensive and bradycardic responses, significantly different from nifedipine-induced (0.5 mg/kg, i.v.) hypotensive and reflex tachycardic effects in pentobarbital-anesthetized Wistar rats. A single oral administration of vanidipinedilol at doses of 10, 25, and 50 mg/kg dose-dependently reduced blood pressure with a decrease in heart rate in conscious spontaneously hypertensive rats (SHRs). In the isolated Wistar rat atrium, vanidipinedilol (10(-7), 10(-6), and 10(-5) M) competitively antagonized the (-)isoproterenol-induced positive chronotropic and inotropic effects and inhibited the increase in heart rate induced by Ca2+ (3.0-9.0 mM) in a concentration-dependent manner. The parallel shift to the right of the concentration-response curve of (-)isoproterenol and CaCl2 suggested that vanidipinedilol possessed beta-adrenoceptor-blocking and calcium entry-blocking activities. On tracheal strips of reserpinized guinea pig, cumulative doses of vanidipinedilol (10(-10) to 3x10(-6) M) produced dose-dependent relaxant responses. Preincubating the preparation with ICI 118,551 (10(-10), 10(-9), 10(-8) M), a beta2-adrenoceptor antagonist, shifted the vanidipinedilol concentration-relaxation curve significantly to a region of higher concentrations. These results implied that vanidipinedilol had a partial beta2-agonist activity. In the isolated thoracic aorta of rat, vanidipinedilol had a potent effect inhibiting high-K+-induced contractions. KCI-induced intracellular calcium changes of blood vessel smooth muscle cell (A7r5 cell lines) determined by laser cytometry also was decreased after administration of vanidipinedilol (10(-8), 10(-7), 10(-6) M). Furthermore, the binding characteristics of vanidipinedilol and various antagonists were evaluated in [3H]CGP-12177 binding to ventricle and lung and [3H]nitrendipine binding to cerebral cortex membranes in rats. The order of potency of beta1- and beta2-adrenoceptor antagonist activity against [3H]CGP-12177 binding was (-)propranolol (pKi, 8.59 for beta1 and 8.09 for beta2) > vanidipinedilol (pKi, 7.09 for beta1 and 6.64 for beta2) > atenolol (pKi, 6.58 for beta1 and 5.12 for beta2). The order of potency of calcium channel antagonist activity against [3H]nitrendipine binding was nifedipine (pKi, 9.36) > vanidipinedilol (pKi, 8.07). The ratio of beta1-adrenergic-blocking/calcium entry-blocking selectivity is 0.1 and indicated that vanidipinedilol revealed more in calcium entry-blocking than in beta-adrenergic-blocking activities. It has been suggested that vanidipinedilol-induced smooth muscle relaxation may involve decreased entry of Ca2+ and partial beta2-agonist activities. In conclusion, vanidipinedilol is a nonselective beta-adrenoceptor antagonist with calcium channel blocking and partial beta2-agonist associated vasorelaxant and tracheal relaxant activities. Particularly, the vasodilator effects of vanidipinedilol are attributed to a synergism of its calcium entry blocking and partial beta2-agonist activities in the blood vessel. A sustained bradycardic effect results from beta-adrenoceptor blocking and calcium entry blocking, which blunts the sympathetic activation-associated reflex tachycardia in the heart.

Coronary spasm masquerading as progressive exertional angina with normal coronaries

A case of typical exertional angina secondary to chronic focal vasospasm with normal coronary arteries and the role of vasospasm in typical angina are briefly discussed. Recommendations are made regarding evaluation of patients with normal coronaries and angina.

Changing concepts in the pathophysiology of myocardial ischemia

The principal common pathway for myocardial ischemia is an oxygen supply-demand imbalance; more recently, greater emphasis has been placed on limitations of myocardial blood supply, as well as excessive myocardial oxygen demand. Myocardial ischemia is a metabolic event resulting from inadequate oxygen delivery to local tissues. The physiologic effects of ischemia are observed through abnormalities in left ventricular function, electrocardiographic changes, and often, by angina pectoris. Prognostic and therapeutic outcomes are significantly related to the pathophysiology of the underlying coronary lesion. Because myocardial ischemia often occurs without symptoms, clinical distinctions based on angina stability may more appropriately be represented by stable or unstable ischemic syndromes that incorporate silent ischemia. Stable ischemic syndromes occur secondary to coronary plaques, whereas unstable syndromes are the result of active lesions caused by plaque rupture with local thrombus and vasoreactivity that produce intermittent critical decreases in coronary supply. The prognosis of patients with stable ischemia is related to the extent of myocardium at jeopardy and overall left ventricular function. In contrast, unstable syndromes are associated with a worse short-term prognosis, which may be predictable by the presence of silent ischemia or left ventricular dysfunction or both. Therapeutic decisions based on an improved pathophysiologic understanding of ischemic mechanisms as well as the physiologic impact of therapy on cardiac function can enhance efficacy while avoiding adverse effects. Calcium channel blockers appear to afford certain advantages in the treatment of myocardial ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective effects of PN 200-110 (isradipine) on the peripheral circulation and the heart

PN 200-110 (isradipine) is a new dihydropyridine calcium antagonist with selective actions on the heart as well as the peripheral circulation. It selectively inhibits the sinus node but not atrioventricular conduction and its negative inotropic action is minimal, about 20 times weaker than its negative chronotropic effect. This in vitro pattern also expresses itself in vivo: partial suppression of the reflex tachycardia induced by its peripheral vasodilatation and no effect on the P-Q interval on the electrocardiogram even at large doses. The presence of first- or second-degree heart block should therefore not limit its use, whereas the sick sinus syndrome might. PN 200-110 does not decrease myocardial contractile force even in vagotomized animals with full beta blockade. PN 200-110 nevertheless lowers myocardial oxygen consumption mainly by its action on afterload. It should therefore be useful in angina pectoris. PN 200-110 is a powerful peripheral vasodilator. It preferentially dilates coronary, cerebral and skeletal muscle vasculature. Its long lasting (24 to 48 hours) antihypertensive action is not accompanied by tachycardia in spontaneously hypertensive rats and it enhances sodium and water excretion in normotensive rats. It should be useful in the treatment of hypertension, and, considering its pattern of cardiac actions, perhaps also as an after-load-reducing agent for the treatment of heart failure. Antiarteriosclerotic effects in conscious rabbits were found at reasonably small doses, suggesting that such effects might occur in man at therapeutic doses.

New therapeutic modalities for the treatment of elderly patients with ischemic heart disease

In developing a treatment plan for elderly patients with ischemic heart disease, it is important to appreciate that the pathophysiologic process and aging influence the type of response produced by various drugs. The aging process also alters the way drugs are absorbed, distributed, and eliminated. Each of these variables must be considered in deciding which drugs should be used and how they should be administered.

Daily variations of ECG and left ventricular parameters at exercise in patients with anginal attacks but normal coronary arteriograms

In 21 patients with typical exercise-induced anginal pain but normal coronary arteriograms (group N) and in 14 patients with angiographically proved coronary stenosis (group C), symptom-limited ergometer exercise ECG and radionuclide angiocardiography were performed twice on two different days. Exercise-induced ST changes showed larger variations between the two exercise tests in group N than in group C ([delta ST1-delta ST2]: 0.07 +/- 0.06 mV in group N, 0.03 +/- 0.03 mV in group C, p less than 0.05). Rate pressure product and left ventricular ejection fraction at exercise also showed larger variations between the two tests in group N than in group C (p less than 0.001, p less than 0.05, respectively). However, substantial overlaps existed in some cases in the two groups. In conclusion, some of the patients with exercise-induced anginal pain but normal coronary arteriograms may have a variable threshold of exertional chest pain probably caused by variation in coronary vascular tone, and the other patients may have a fixed threshold of chest pain caused by other mechanisms.

Effects of diltiazem on regional coronary hemodynamics during atrial pacing in patients with stable exertional angina: implications for mechanism of action

To investigate the mechanism of the antianginal action of diltiazem in stress-induced myocardial ischemia, we studied 12 patients with stable exertional angina and disease of the proximal left anterior descending artery by measuring great cardiac vein flow (GVCF) and calculating anterior regional coronary resistance (ARCR) during myocardial ischemia induced by atrial pacing before and after intravenous administration of diltiazem (0.25 mg/kg in a bolus dose followed by continuous infusion of 0.005 mg/kg/min). Diltiazem increased the pacing time to angina from 6.9 +/- 3.5 to 10.7 +/- 4 min (p less than .001). At peak pacing heart rate was increased after diltiazem (from 128 +/- 17 to 145 +/- 17 beats/min, p less than .005), while mean arterial pressure was decreased (from 131 +/- 19 to 113 +/- 17 mm Hg, p less than .025), leaving the double product unaltered. At peak pacing no changes were observed in GCVF (from 115 +/- 46 to 119 +/- 46 ml/min, p = NS), ARCR (from 1.3 +/- 0.4 to 1.1 +/- 0.4 mm Hg/ml/min), or myocardial oxygen consumption of the anterior region (from 14.5 +/- 4.2 to 13.4 +/- 4.7 ml/min). Reduction of myocardial oxygen demand plays a major role in the antianginal action of diltiazem in patients with stress-induced myocardial ischemia.

Factors determining the activity of ischemic heart disease

Transient regional myocardial ischemia appears to underlie symptoms such as angina pectoris and represents a key pathophysiologic step, since it is an objective marker of disease activity and is capable of causing disabling symptoms and damage to left ventricular myocardium. A study of the characteristics of transient ischemia in and out of the hospital has shown that symptoms are an inconsistent underestimation of these events. Ischemia is generally prolonged, mostly asymptomatic, and usually accompanied by a regional decrease in myocardial perfusion. Studies out of the hospital have also shown that these episodes are frequently triggered by a wide range of ordinary everyday activities. These new features of transient ischemia are worth noting when searching for relevant causes that are present during everyday life and when trying to choose more rational therapy. More detailed studies of patient activity have shown that different levels of mental arousal are the most common triggering mechanism causing ischemia out of the hospital. In addition, the occurrence of transient ischemia during everyday life displays a circadian rhythm, with an increase and peak occurrence between 6:00 A.M. and 12 noon each day. The day-to-day variability of ischemia is marked, indicating functional disturbances of coronary stenoses against a background of a severe reduction in cross-sectional area. The examination of proximal stenoses has shown that the reduction in cross-sectional area is usually underestimated by conventional angiography; pressure gradients across coronary stenoses are common and, with reduced poststenotic blood pressure, can jeopardize perfusion; disturbances of vessel caliber and antegrade flow can accompany many of the ordinary everyday activities known to trigger ischemia detected in Holter tapes studied out of the hospital; and there is clear-cut evidence of endothelial dysfunction in these patients, with reversal of the normal dilator response to acetylcholine and paradoxical constriction of stenoses. This evidence of endothelial dysfunction in humans could be central to the problems of atheromatous narrowing, thrombus, and disturbed vasomotion.

Cigarette smoking during coronary angiography: diffuse or focal narrowing (spasm) of the coronary arteries in 13 patients with angina at rest and normal coronary angiograms

To evaluate the acute effects of cigarette smoking on coronary arteries (CA), repeated coronary angiograms were performed in 13 patients with angina at rest and with normal coronary angiograms at basal state, during smoking, and then after methylergometrine (MEM) and after intracoronary nitroglycerin. Smoking induced anginal pain in three patients, triggered spasm (focal narrowing) in six, and/or an abnormal segmental diffuse narrowing (greater than 30%) in eight. The narrowing of the left CA was on average -21 +/- 13% (P less than 0.001), with more important narrowing of the mid-left anterior descending (-29 +/- 19%, P less than 0.001). The mean of the maximal segmental narrowing by patient was -34 +/- 13% (P less than 0.001). MEM produced similar effects and induced focal CA spasms in nearly the same patients at the same sites. Cigarette smoking may induce vasoconstrictive effects on CA in patients with rest angina and normal coronary angiograms. This action is not dose-dependent and may be initiated by less than one cigarette. These observations offer a new perspective for the understanding of the role of smoking in the precipitation of coronary events.