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Patients with AMI and AF/FL portend a poor prognosis in the long-term chiefly because of an excess of SD. Treatment with ACE-inhibitors and digitalis may have long-term beneficial effects on SD.

Aortic intramural hematoma (IMH) is a rarely diagnosed pathological condition that is not well characterized to date. We diagnosed IMH in 4 of 31 patients with suspected aortic dissection admitted to our coronary care unit from 1992 to 1995. In all 4 cases, IMH was located in the ascending aorta. At the time of hospitalization, all patients showed tachycardia, hypotension and pericardial effusion. Diagnosis of IMH was made by transesophageal echocardiography and computed tomography. We performed aortography in 2 patients, but it was non-diagnostic in both of them. One patient died before surgery. Autopsy confirmed the diagnosis of IMH and showed severe pericardial effusion. In another patient, the diagnosis was confirmed during successful surgery, while the remaining 2 patients recovered after medical therapy. The 3 surviving patients are still under follow-up control 12, 16 and 20 months after the initial acute event. We briefly discuss the epidemiological, clinical, diagnostic, therapeutic and prognostic aspects of IMH.

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The majority of calcium antagonists used clinically belong to three distinct chemical classes: the phenylalkylamines, the dihydropyridines, and the benzothiazepines. In recent years their mode of action has been unravelled, their limitations recognized, and their efficacy and use in the management of patients with a broad spectrum of cardiovascular and other disorders defined. It is clear, however, that these drugs are not all alike, providing an explanation for their differing effects. The final therapeutic effect in humans depends on the mechanisms of action at the molecular level, the tissue selectivity, and the hemodynamic changes of each agent. All these aspects are examined in detail in this article. Concepts that are highlighted are as follows: (a) Molecular biology has allowed recognition of the polypeptide components of the alpha 1 subunit of the L-type Ca2+ channel and the finding of peptide segments covalently labelled by all three classes of drugs. (b) The location of these segments within the peptides is different: Binding sites for dihydropyridines are located externally, whereas those for verapamil and diltiazem are located internally, in the cytosolic part of the membrane. (c) Dihydropyridine binding is voltage dependent. This explains the selectivity of this class of drugs for vascular smooth muscle, which is more depolarized than cardiac muscle. (d) Phenylalkylamines and benzothiazepines reach their receptors at the internal surface of the sarcolemma through the channel lumen. Their binding is facilitated by the repetitive depolarization of atrioventricular and cardiac tissue, a phenomenon described as use dependence. This explains why these drugs are not highly selective, but equipotent for the myocardium, the atrioventricular conducting tissue, and the vasculature. (e) Dihydropyridines act through selective vasodilatation and may increase heart rate and contractility via a reflex mechanism. On the contrary, phenylalkylamines and diltiazem act through a combination of effects, including reduction of afterload, heart rate, and contractility. When taken together, all these differences distinguish the preferential clinical utilization of one of these compounds for a given cardiovascular pathology.

The pharmacokinetics of ajmaline were studied in 10 patients with suspected paroxysmal atrioventricular block who received a 1 mg/kg intravenous dose over 2 minutes for diagnostic purposes (ajmaline test). Plasma concentration decay followed a triexponential time course with a final half-life much longer (7.3 +/- 3.6 hours) than that previously found by other investigators (about 15 minutes). Mean total plasma clearance and renal clearance were 9.76 ml/min/kg and 0.028 ml/min/kg, respectively. Although most of the dose was eliminated through the extrarenal route (only 3.5% of the intravenous dose was recovered in urine), no fluorescent metabolites could be detected either in plasma or urine. The steady-state volume of distribution averaged 6.17 L/kg, and plasma protein binding ranged between 29 and 46%. Three patients developed a transient atrioventricular block after ajmaline administration. In the remainder, the drug prolonged atrio-His bundle (AH interval), His bundle-ventricular (HV interval) and intraventricular (QRS interval) conduction times. Corrected ventricular repolarisation time (QTc interval) showed less marked changes, which were biphasic at times. The mean maximum ajmaline-induced increase in HV interval was 98%, in QRS was 58%, in AH was 30%, and in QTc was 17%. In most cases the time course of electrocardiographic changes lagged behind that of plasma concentrations, suggesting a delayed equilibrium of plasma concentrations with the site of action (hysteresis). Despite that, the pharmacokinetic-pharmacodynamic model, which accounted for hysteresis, failed to fit the experimental data adequately.(ABSTRACT TRUNCATED AT 250 WORDS)

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