Use and safety of acellular pertussis vaccine among adult hospital staff during an outbreak of pertussis

During May and June 1993, 10 patients and 5 members of the clinical staff at a hospital in California were diagnosed with Bordetella pertussis infection. In addition to erythromycin prophylaxis, 630 (48%) of 1330 staff members received a half dose of acellular pertussis vaccine with tetanus and diphtheria toxoids (DTaP). To identify side effects of the vaccine, a questionnaire was completed by 344 (54%) of 630 vaccinated staff. Side effects were reported by 117 respondents (34%); 64 were classified as mild (local reaction at injection site) and 50 as moderate (systemic complaints or local reaction resulting in limitation of arm movement). Three vaccinees (< 1%) reported missing 1 or more days of work because of their symptoms. Local reactions at the injection site occurred in 100 (29%), systemic symptoms in 38 (11%), and limitation of arm movement in 18 (5%). This study indicates that use of half dose of DTaP in adults appears safe and should be considered as an adjunct to chemoprophylaxis during institutional outbreaks.

The effect of quinidine and myocardial ischemia on the isolated rat heart with fat-free diet

Fat-free diet changes the lipid content and the electrophysiological properties of the rat myocardium. Five percent fat supplementation to the diet does not alter the basic electrophysiological properties but still has a biochemical effect on the lipid content of the myocardium. The purpose of this work was to determine whether these biochemical alterations affect the response of the myocardium to quinidine and ischemia, both of which interact with the lipid component of the membrane. We used strength-duration, strength-interval and threshold of ventricular fibrillation to measure the electrophysiological properties of the isolated rat heart at baseline and after 30 minutes of quinidine perfusion or coronary artery ligation. The fatty acid composition of the myocardium was analyzed. We found that a fat-free diet caused essential fatty-acid deficiency, while 5% fat supplementation had a partial protective effect. Quinidine decreased excitability and increased refractoriness in both groups but had more effect on the fat-free diet hearts group. There was no difference in the ventricular fibrillation threshold. Ischemia increased myocardial excitability in the fat-free diet hearts group and had no effect on refractoriness or ventricular fibrillation threshold. These results support the theory that the lipid composition of the myocardial membrane affects its response to lipophilic drugs and ischemia.

Percutaneous excimer laser coronary angioplasty of lesions not ideal for balloon angioplasty

BACKGROUND

Excimer laser coronary angioplasty is a new, investigational technique for treating coronary artery stenoses. Initial reports have demonstrated acute efficacy and relative safety of this procedure, but have not addressed the effect of lesion type on acute success and complication rates.

METHODS AND RESULTS

In the first 100 patients undergoing percutaneous excimer laser coronary angioplasty at our institution, acute laser success was obtained in 84% and procedural success was obtained in 94%. There were six acute closures during laser angioplasty and one myocardial infarction. Two patients required emergency coronary bypass surgery. Sixty-five percent of patients had lesions not ideal for balloon angioplasty because of lesion morphology (tubular, diffuse, or chronic total occlusion) or ostial location. There were 10 tubular stenoses, 29 diffuse lesions, 18 chronic total occlusions, and eight ostial lesions, including five aorto-ostial lesions. In this nonideal subgroup, the acute success rate with laser was 86% (72% of chronic total occlusions and 91% of non-totally occluded lesions), and the procedural success rate was 94%. There were three acute occlusions during laser angioplasty but no myocardial infarctions, emergency bypass surgeries, or deaths. One coronary artery perforation occurred without clinical sequelae. Laser angioplasty was successful in four of six lesions (67%) in which balloon angioplasty had failed. Laser success was obtained in 10 of 11 (91%) moderately or heavily calcified stenoses. Eight eccentric lesions and two lesions on bends were successfully treated without dissection or perforation. No side branch occlusions occurred in the 15 patients in whom one or more major branches originated within the lesion treated. Adjunctive balloon angioplasty was performed in 47% of cases, usually to obtain a larger final luminal diameter. Need for adjunctive balloon angioplasty decreased to 36% after a larger (2.0 mm) laser catheter became available. Twenty-eight percent of the 105 lesions treated were American College of Cardiology/American Heart Association classification type A, 47% were type B, and 25% were type C. Laser and procedural successes were obtained in 83% and 97% of type A, 88% and 96% of type B, and 85% and 88% of type C lesions, respectively.

CONCLUSIONS

In our initial experience, excimer laser angioplasty was found to be acutely effective and safe therapy for lesions identified as not ideal for balloon angioplasty. This technique may provide a useful adjunct or alternative to balloon angioplasty in selected patients.

Nitrate tolerance in heart failure: differential venous, pulmonary and systemic arterial effects

The hemodynamic profile of tolerance to intravenous nitroglycerin was studied in 9 patients with New York Heart Association Class III to IV congestive heart failure. After rapid dosage build-up to the maximal tolerated dose (decrease in pulmonary wedge pressure to 10 mm Hg or systolic blood pressure to 90 mm Hg), nitroglycerin (525 +/- 548 micrograms/min) was administered at a constant continuous intravenous infusion for a total of 24 hours. The extent of nitrate tolerance at 24 hours was calculated as the percentage loss of the benefit achieved at time of peak effect of nitroglycerin. Tolerance had a different time course and magnitude in the venous, arterial and pulmonary circulations. At 24 hours, right atrial pressure and pulmonary vascular resistance returned to control values in most patients, while 40 to 50% of the effect on systemic vascular resistance, cardiac index and pulmonary wedge pressure was maintained. These findings emphasize the importance of precise definitions in studies relating to nitrate tolerance.

Predicting late restenosis after coronary angioplasty by very early (12 to 24 h) thallium-201 scintigraphy: implications with regard to mechanisms of late coronary restenosis

To examine whether late coronary restenosis may be predicted by abnormalities of myocardial perfusion in the early hours after successful percutaneous transluminal coronary angioplasty and to study in greater detail the mechanisms involved in the development of late coronary restenosis after angioplasty, a prospective study was undertaken in 90 consecutive patients. Thallium-201 scintigrams were recorded at rest and during the stress of atrial pacing, 12 to 24 h after angioplasty, and the results were related to the findings at angiography in 70 patients undergoing late cardiac catheterization. A reversible thallium-201 perfusion defect was found in 39 (38%) of 104 myocardial regions supplied by the dilated coronary vessel and identified a subset of patients at high risk of late (6 to 12 months) angiographic restenosis (sensitivity 77%, specificity 67%). In contrast, late coronary restenosis developed in only 7 (11%) of 65 vessels and in 5 (14%) of 37 patients with a nonischemic thallium-201 scintigram on day 1 (p less than 0.005). Multivariate logistic regression analysis of 14 possible preangioplasty and periangioplasty clinical and angiographic variables selected reversible perfusion defect on the thallium-201 scintigram on day 1 (p = 0.016) and immediate postangioplasty residual coronary narrowing (p = 0.004) as significant independent predictors of late restenosis, with younger patient age as an additional less powerful predictor (p less than 0.05). The findings have important implications regarding the pathogenesis of late coronary restenosis in patients undergoing successful angioplasty and they imply that in the majority of these patients pathophysiologic events in the early minutes and hours after angioplasty may determine the development of late restenosis.

Effect of the second-generation calcium channel blocking drug nisoldipine on diastolic left ventricular dysfunction in heart failure

The effect of intravenous nisoldipine (0.12 microgram/kg/min) on diastolic left ventricular (LV) dysfunction was studied from simultaneous hemodynamic and radionuclide measurements in 12 patients with New York Heart Association class II to IV cardiac failure. The initial LV filling fraction was low, the peak LV filling rate normalized for end-diastolic volume was decreased, and the pulmonary capillary wedge pressure (PCWP) was high and associated with clinical shortness of breath. Nisoldipine produced an increase in LV filling fraction from 36 +/- 17% to 43 +/- 20% (p = 0.003). The increase in filling took place in both early and late diastole: peak early filling rate (PFR) increased in 11 of the 12 patients (p = 0.02) and late diastolic filling rate (atrial [A] wave in eight of them (NS). When the determinants of these changes, were examined further, it was found that in the control state PFR was inversely related to LV end-systolic volume (r = 0.77), whereas the A wave was related in exponential fashion to PCWP (preload) (r = 0.79). Nisoldipine did not change the slope of these relationships, and it did not alter the end-diastolic pressure-volume relationship, implying that inherent myocardial relaxation and distensibility were unaltered by the drug. In summary, nisoldipine improved measurements of diastolic LV dysfunction in patients with cardiac failure. This study illustrates the importance of considering ventricular loading conditions when analyzing and interpreting measurements of diastolic ventricular dysfunction. The measured changes in diastolic LV function during infusion of nisoldipine appear to be due to alterations in ventricular loading conditions rather than to a direct myocardial effect of the drug.

Identifying patients at high risk for restenosis after percutaneous transluminal coronary angioplasty for unstable angina pectoris

To study the determinants of late restenosis after percutaneous transluminal coronary angioplasty (PTCA) performed in patients with unstable angina pectoris, a prospective study was undertaken in 90 patients. Primary PTCA success was achieved in 84 (93%) patients, dilating 116 of 118 coronary narrowings (1.4/patient), while major complications during PTCA occurred in only 1 patient (1 death). Eighty-two patients (114 dilated arteries) were followed for 25 +/- 11 months: 68 (83%) were in New York Heart Association functional class I or II, 11 (13%) in class III, and there were 3 deaths. Late restenosis was found in 16 (25%) of 65 lesions (29% of 49 patients) studied by angiography 9 +/- 7 months after PTCA. Restenosis was more frequent in left anterior descending coronary artery lesions (p = 0.07) and in those which at the time of PTCA had multiple irregularities (67 vs 14%, odds ratio 12.5, p = 0.002), decreased coronary perfusion (Thrombolysis in Myocardial Infarction grade less than 3) (50 vs 15%, odds ratio 5.7, p = 0.02) or intraluminal thrombus (67 vs 19%, odds ratio 8.7, difference not significant). Multiple irregularities (p = 0.003) and decreased flow (p = 0.02) remained independent predictors of restenosis (goodness of fit 0.88) after adjustment for 12 pre- and peri-PTCA clinical and angiographic variables by logistic regression analysis. These data underline the feasibility of early revascularization by PTCA in patients with unstable angina pectoris. Careful follow-up should be instituted in patients with multiple irregular lesions, decreased coronary perfusion or intraluminal thrombus at the time of PTCA. In such patients, late restenosis may be the rule rather than the exception.

[Percutaneous transluminal coronary angioplasty after coronary artery bypass]

Anginal syndrome may recur early of several years after coronary artery bypass surgery (CABS), and may be due to narrowing of a bypass graft, progression of pre-existing coronary artery lesions, or the appearance of new lesions. Repeat CABS is associated with considerable morbidity and mortality. We therefore performed percutaneous transluminal angioplasty (PTCA) in saphenous or internal mammary bypass grafts or native coronary arteries in 23 patients after CABS. We successfully dilated 35 of 37 lesions (95%) present in 33 of 35 vessels (94%) of 21 of 23 patients (91%). The mean vessel narrowing decreased from 86 +/- 22% to 13 +/- 19% (p less than 0.001) and in all 21 patients with angiographic evidence of success functional capacity improved. Single vein grafts were successfully dilated in 9 patients. None developed acute myocardial infarction or needed emergency surgery, but 1 had a cerebral embolism. PTCA is effective therapy for recurrent angina after CABS, and in many patients is preferable to another operation.

Persistent painless ST-segment depression after exercise testing and the effect of age

The relation between the duration of ischemic ST-segment depression (1 mm or more 60 ms after the J point) and the clinical awareness of chest pain was studied in 31 patients (aged 39-73 years) undergoing symptom-limited, graded treadmill exercise testing. The response of these patients to nitrate therapy (spray or sublingual tablet) given immediately on cessation of exercise was also studied. During exercise, angina pectoris appeared at an estimated workload of 4.6 +/- 2.2 metabolic equivalents (METS) (mean +/- SD), and pathological ST-segment depression at 4.9 +/- 1.9 METS (p = NS.) On cessation of exercise, angina disappeared after 3.0 +/- 1.9 min, but ST-segment depression persisted for more than twice as long (6.6 +/- 4.1 min) (p less than 0.0001). The ratio of time to ST-segment recovery/time to relief of pain (a quantitative measure of silent ischemia during recovery) increased with age (r = 0.49, p = 0.002), and in 16 patients over 60 years of age was higher than in 15 younger patients (3.6 +/- 2.5 vs. 2.1 +/- 1.4) (p less than 0.04). The silent ischemia ratio after exercise tended to decrease, although not significantly so (p = 0.2), in patients who received oral nitrates; there was no difference in the response to spray or tablet in this regard. We conclude that ST-segment depression frequently persists after relief of exercise-induced angina pectoris and more so in elderly patients.

Effect of the second-generation calcium channel blocker nisoldipine on left ventricular contractility in cardiac failure

We studied the acute effects of nisoldipine, a new second-generation calcium channel-blocking drug, on cardiac hemodynamics and left ventricular (LV) contractility in 10 patients with grade 2 to 4 cardiac failure. Pressures were measured from an arterial line and a flow-guided catheter in the pulmonary artery, cardiac output by thermodilution, and LV ejection fraction simultaneously by radionuclide ventriculography. Ventricular loading conditions were altered by sublingual nitroglycerin to facilitate construction of LV end-systolic pressure (radial stress)-volume and stress-shortening curves. Nisoldipine, given by continuous intravenous infusion (0.12 micrograms/kg/min), reduced mean arterial pressure (p = 0.001), systemic vascular resistance (p less than 0.05), and the double product, a measurement of myocardial oxygen demand (p less than 0.01). Cardiac index, stroke index, and LV ejection fraction increased in 8 of the 10 patients. LV contractility was initially greatly reduced and was unchanged or slightly decreased during the administration of nisoldipine. Emax, the slope of the end-systolic pressure-volume curve, was unaltered in half of the patients and decreased in the others (NS), whereas the end-systolic stress-shortening curve did not change. In summary, nisoldipine has a potentially useful acute hemodynamic profile in patients with cardiac failure; it increases forward blood flow in most patients, decreases the determinants of myocardial oxygen demand, and produces little measurable changes in the inotropic state of the left ventricle.

Dietary lipid intake and myocardial electrophysiology

We studied the effect of a fat-free diet on the cardiac electrophysiology of rats. Fourteen 2-week-old rats were maintained on a fat-free diet and 12 rats had a 5% soybean oil supplement to their diet. The rats were killed after 6 weeks and the hearts mounted on a Langendorff chamber. Atrioventricular (A-V) block was induced. Myocardial strength-duration (S-D) and strength-interval (S-I) curves were determined. A significant depletion of linoleic acid and elevation of palmitoleic, stearic, and oleic acids was found in the hearts obtained from rats on fat-free diet as compared with the hearts obtained from the rats on oil-supplemented diets. Hearts obtained from rats who had had the oil supplement had a shorter refractory period and an increased threshold for excitation; therefore, these hearts should be less vulnerable to cardiac dysrhythmias. Both S-D and S-I curves best fitted a logarithmic relationship. The intercepts and slopes of these curves were significantly different in the two groups. There were significant correlations between myocardial fatty acid composition (stearate and linoleate in particular) and the different electrophysiological parameters.

Prediction of atrial and ventricular fibrillation complicating myocardial infarction from admission data: a prospective study

This study set out to examine prospectively two logistic formulae based on admission clinical data to predict ventricular or atrial fibrillation complicating acute myocardial infarction. A prospective study of 87 consecutive patients with acute transmural myocardial infarction was conducted. The formula for predicting ventricular fibrillation from the diastolic blood pressure, degree of ST-segment elevation, and QTc had a sensitivity of 93%, specificity of 83%, and a predictive value for an abnormal test of 62% (13 of 14 patients who developed ventricular fibrillation were identified). The formula for predicting atrial fibrillation from the age of the patient, a history of heart failure, systolic blood pressure, and four electrocardiographic parameters had a sensitivity of 78%, specificity of 85%, and a predictive value of 67% (14 of 18 patients identified). Our study shows that patients with myocardial infarction who are liable to develop ventricular or atrial fibrillation can be identified on admission from simple clinical data.

Fat-free diet and myocardial excitability, refractoriness and ventricular fibrillation

The lipid composition of the sarcolemma influences its function. The purpose of this study is to investigate the electrophysiological alterations induced in the rat's heart by dietary manipulation of cardiac fatty-acid composition. Strength-duration and strength-interval relationships were used to study excitability and refractoriness respectively. Ventricular fibrillation threshold measured by short bursts of rapid stimulation was used to indicate ventricular vulnerability. Gas liquid chromatography was used to analyse cardiac fatty-acid-composition. We used two-week-old rats fed with fat-free diet and 5% and 10% soya bean oil-supplemented diets for 6-9 weeks. Fat-free diet only was associated with increased eicosatrienoic acid content, a marker of essential fatty-acid deficiency. A decrease in poly-unsaturated to saturated (P:S) fatty-acid ratio was also observed. Five percent oil supplementation was associated with a delay and attenuation of this effect. Fat-free diet was associated with increased excitability, decreased refractoriness and reduced ventricular fibrillation threshold. Ten percent oil supplementation prevented these effects while 5% oil supplementation had only a temporary protective effect. We conclude that manipulation of dietary fat content can affect cardiac fatty-acid composition and electrophysiology.

Effects of vitamin A and dexamethasone on capsule collagen metabolism in mouse mammary adenocarcinoma

It was previously shown that the administration of dexamethasone (Dex) to mice bearing mammary adenocarcinoma caused the collagen content of the tumor capsule to be decreased by 50%, but collagenase and other neutral protease activities of the tumor were the same as in the controls. These events occurred with distinctly increased tumor invasion and metastasis. The present communication reports on the characterization of capsule collagen and the effects of agents [vitamin A (VA) and Dex] on capsule collagen metabolism and presents further evidence concerning the possible mechanisms by which the collagen content of the capsule was decreased in the Dex-treated hosts. The collagen extracted from capsules of untreated controls and mice (C3H/HeJ) treated with VA or Dex was primarily type I, as judged by the migration of protein bands in sodium dodecylsulfate-polyacrylamide gel electrophoresis and by patterns of elution peaks from an octadecyl C-18 column. The amino acid compositions of type I collagen of the capsule of treated and untreated controls were similar but not identical to those of mouse skin and guinea pig skin type I collagens. The specific activity of intracellular free [14C] proline, the extent of hydroxylation of [14C]proline residues of collagen, and the specific activity of [14C]hydroxyproline and proline in each case were similar in treated and in untreated controls. These results suggest that the observed 45% decrease in the conversion of [14C]proline into protein-bound [14C]hydroxyproline of the Dex-treated hosts apparently was due to decreased collagen synthesis. The data also suggest that the most critical effects of Dex on tumor invasion and metastasis appeared to occur at an early stage before full formation of the collagenous extracellular matrix.

Left ventricular function during physiological cardiac pacing: relation to rate, pacing mode, and underlying myocardial disease

The hemodynamic effects of cardiac pacing at different rates and in different modes were studied in 21 patients who were candidates for permanent pacemaker implantation. Nine of these had primary conduction disturbances (PCD), ten had ischemic heart disease (IHD), seven with additional cardiac failure (CHF), and two had hypertrophic cardiomyopathy (HCM). In patients with PCD, atrial (AOO) and AV sequential (DVI) pacing did not change systolic blood pressure and pulse pressure but ventricular (VVI) pacing caused a progressive fall in these measurements, especially as heart rate increased. Ventricular volume and stroke volume (counts) derived from radionuclide ventriculography (RVG) decreased progressively with higher pacing rates, especially during VVI pacing. Cardiac output was maintained during VVI pacing by the increase in heart rate; during AOO and DVI pacing, cardiac output increased. Similar but more marked differences were observed in patients with IHD and CHF and the changes were even greater in the patients with HCM. Left ventricular (LV) ejection fraction changed little with increasing heart rate in PCD but decreased progressively with the onset of ischemia in IHD and CHF. There was no difference in ejection fraction in the different pacing modes. Graphs related to LV contractility (end-systolic pressure-volume relations) showed that AOO pacing produced the highest and VVI pacing produced the lowest curves of myocardial contractility in all patient groups, except that at higher rates the AOO curve shifted down again in patients with IHD and CHF, presumably with the onset of myocardial ischemia. This study showed that physiological pacing produced the best hemodynamic results in all patient groups. Higher pacing rates should be avoided in patients with ischemic heart disease while VVI pacing should not be used in patients with HCM. Blood pressure and RVG studies during temporary pacing are useful in selecting the optimal pacing system in an individual patient when the clinical choice is not clear.

Chronotropic effect of hydralazine and its mechanism of symptomatic sinus bradycardia

The positive chronotropic effect of hydralazine was studied in 9 patients with symptomatic sinus bradycardia. Hydralazine was given in an intravenous dose of 0.15 mg/kg and heart rate, blood pressure, sinoatrial conduction time (Narula method) and corrected sinus node recovery time were measured. The effect of hydralazine was also studied after total autonomic nervous system blockade using 0.04 mg/kg of atropine and 0.2 mg/kg of propranolol intravenously. In the control state hydralazine produced an increase of 28 +/- 15% (mean +/- standard deviation) in heart rate, and this was essentially due to a decrease in sinoatrial conduction time (by 32 +/- 32%, p less than 0.05). Corrected sinus node recovery time also tended to shorten (decrease of 21 +/- 34%, difference not significant). After total autonomic blockade intrinsic heart rate did not change or increased very little (9 +/- 14%) after administration of hydralazine and there was no consistent change in sinoatrial conduction and corrected sinus node recovery times. The small residual effect of hydralazine on heart rate was related to incomplete autonomic blockade, since the effect of postural change (standing) on heart rate was also not totally abolished. The study showed that the positive chronotropic effect of hydralazine was mainly due to a change in sinoatrial conduction with a smaller change in corrected sinus node recovery time, and the major chronotropic effect of the drug was mediated by the autonomic nervous system.

Left ventricular function from end-systolic stress-shortening relations in mitral valve prolapse

Left ventricular (LV) function was studied from end-systolic stress-shortening relations in 13 patients with mitral valve prolapse (MVP). Studies were made noninvasively using M-mode echocardiography with blood pressure measurements on the right arm from a Baumanometer cuff. Fifteen age and sex-matched normal subjects formed the control group. LV end-diastolic dimension was normal in MVP, while shortening fraction (p less than 0.05) and velocity of circumferential fiber shortening (mean Vcf) in the short axis of the ventricle were increased (p less than 0.05). Ventricular afterload, as measured by meridional end-systolic stress was reduced in MVP (p less than 0.01) but the slope of the stress-shortening curve was not different form normal. The decrease in end-systolic stress was related to the severity of prolapse (r = 0.63, p less than 0.05). The study implied that mid- or basal LV contractility was normal in MVP. The increased shortening fraction of the LV minor axis was in keeping with geometrical changes and a reduced ventricular afterload.

Left ventricular function in acute myocardial infarction: assessment by nuclear angiography

Left ventricular function was assessed in 38 patients two to six days after acute myocardial infarction using nuclear angiocardiography and the following parameters were measured: Left ventricular end-diastolic (LVEDV) and end-systolic volumes (LVESV), ejection fraction (LVEF), indices of left ventricular filling and emptying, right ventricular ejection fraction and ejection rate. Their clinical significance was assessed by their relationship to the patients site and size of infarction, functional capacity, morbidity and mortality. The most sensitive indices of depressed left ventricular function were the EF and ESV. Thus, function was preserved in patients with a small inferior infarction (LVEF = 0.57 +/- 0.07, LVESV = 69 +/- 14 ml) and in Killip Class I (LVEF = 0.48 +/- 0.13, LVESV = 80 +/- 20 ml). Function was disturbed most in patients with extensive anterior infarction (LVEF = 0.18 +/- 0.12, LVESV = 131 +/- 46 ml), Killip Class IV (LVEF = 0.13 +/- 0.07, LVESV = 160 +/- 35 ml), cardiogenic shock (LVEF = 0.14 +/- 0.07, LVESV = 160 +/- 35 ml), pulmonary edema (LVEF = 0.11 +/- 0.06, LVESV = 166 +/- 25 ml) and pulmonary capillary wedge pressure greater than 20 mm Hg (LVEF = 0.14 +/- 0.07, LVESV = 160 +/- 33 ml). Previous infarction was associated with LV dilatation and a greater LVEDV. A lower ejection fraction signified a large infarct and poor left ventricular function. If the ejection fraction was less than 0.15, the patients were unlikely to leave the hospital alive, or if less than 0.25, they were left with poor residual ventricular function and either had significant cardiac failure or high late mortality. Nuclear angiocardiography was a simple method of predicting the clinical pattern and prognosis in each patient and emphasized the importance of limiting infarct size in acute myocardial infarction.

Atrial fibrillation in acute myocardial infarction

Atrial fibrillation (AF) complicating acute myocardial infarction (AMI) is associated with increased morbidity and mortality. Early intervention with antiarrhythmic treatment and hemodynamic support in patients prone to develop AF may modify their course. The purpose of this study was to characterize on admission the patients with AMI who are prone to develop AF. The admission data of 45 consecutive patients who developed AF during the course of AMI, and the data of a control group of 45 consecutive patients with AMI who did not develop AF, were analyzed using logistic regression. The following characteristics of patients who developed AF were identified: old age, history of heart failure prior to admission, low systolic blood pressure on admission, wide P waves, presence of left bundle branch block or left anterior hemiblock, marked ST segment elevation, and PQ segment depression (admission ECG). The logistic regression formula correctly classified 80 of the 90 patients (89%) to their actual group. The study showed that the relative risk of a patient with AMI to develop AF can be estimated on admission from simple, readily available, clinical data.

Short-term effect of nifedipine on effort tolerance in patients with angina pectoris

The short-term effect of oral nifedipine on effort tolerance was tested in 10 patients with effort angina pectoris and a positive effort test (GXT). The patients had four symptom-limited GXTs, using the Bruce protocol, on each day of the study at 0800, 1000, 1400, and 1800 hours. They received four doses of 10 mg oral nifedipine on one day and four doses of placebo on the other, each dose given half an hour prior to each GXT. Values with nifedipine were compared to values with placebo at the same time during each day. Nifedipine improved effort tolerance by 0.5 +/- 0.6 min (p = NS) on the first GXT (mean +/- SEM), by 1.2 +/- 0.6 min (p = NS) on the second GXT, by 1.0 +/- 0.3 min (p less than 0.01) on third GXT, and by 1.3 +/- 0.3 min (p less than 0.01) on the fourth GXT. Improvement of effort tolerance was associated with a fall in resting blood pressure and less ST depression; these changes were statistically significant only on the fourth GXT, which may indicate a cumulative effect of subsequent doses of nifedipine.

The effects of m-AMSA on rat isolated heart

m-AMSA (4'[9-acridinylamino]methansulphon-m-anisidide) is a new cytoxic agent now under clinical trial. We used the rat isolated perfused heart model in order to investigate the cardiac effects of m-AMSA. The results of the dose-response study indicate that m-AMSA has an acute moderate negative inotropic effect. The 90% effect (25% decrease in developed force compared to the control) was observed at drug concentration of 1.5 micrograms/ml. The refractory period (as measured by stimuli of twice diastolic threshold intensity) increased progressively as the drug concentration was increased (up to 2.5 micrograms/ml). Measurements of the strength-duration and strength-interval relationship showed that m-AMSA induced a significant reduction (P less than 0.005) in excitability and prolongation of refactoriness. We suggest that m-AMSA has a membranal cardiotoxic effect in addition to its known intracellular cytotoxic effect.

Effect of sustained release isosorbide dinitrate on exercise performance

The duration of action and hemodynamic mechanisms of isosorbide dinitrate in a sustained release formula (ISDSR) were examined over a 24-hour period. 20 patients with effort angina pectoris were divided randomly into two groups, one group received a single dose of 40 mg ISDSR (at 07.30 h) and the other, two doses of 40 mg ISDSR (at 07.30 and 13.30 h). Every patient had four exercise tests on the first (placebo) day and second (ISDSR) day and a single test on the third (placebo) day. Effort tolerance was improved significantly (p less than 0.05) with ISDSR and this lasted for more than 10 h. The double product was compared to ISDSR. Improvement was achieved by a decrease in blood pressure and an increase in heart rate. There were no signs of increased ischemia (ST segment depression) with the prolongation of exercise time. The antianginal and hemodynamic effects of ISDSR were more pronounced in the patients who received two doses of ISDSR. Thus, ISDSR improved effort tolerance for a prolonged period by inducing a sustained decrease of blood pressure and increase in heart rate in patients with effort-induced angina pectoris.

Restoration and maintenance of sinus rhythm after mitral valve surgery for mitral stenosis

The preoperative clinical, echocardiographic, hemodynamic and surgical data were studied from 40 consecutive patients with pure mitral stenosis and chronic atrial fibrillation who underwent surgical correction of mitral stenosis. After surgery, the patients had cardioversion of atrial fibrillation. The data of 24 patients who maintained sinus rhythm (SR) for more than 3 months (success group) were compared with the data of the 16 patients who failed to maintain SR for more than 3 months (failure group). The patients in the success group were younger (mean age 38 +/- 12 vs 47 +/- 13 years, p less than 0.05), had symptoms for a shorter time (3.0 +/- 4.3 vs 6.4 +/- 5.0 years, p less than 0.02) and had a smaller preoperative echocardiographic left atrial (LA) size (4.9 +/- 0.9 vs 5.5 +/- 1.0 cm, p less than 0.03). The correlation between duration of SR after cardioversion (range 0 to 12 months) and the preoperative data were examined with the use of the "all-possible-subsets-regression" software. The best subset of predictors of successful cardioversion included echocardiographic LA size, functional capacity, duration of symptoms and echocardiographic left ventricular fractional shortening. Patients with symptoms for more than 3 years and echocardiographic LA size of more than 5.2 cm had low rate of successful cardioversion; in this subset of patients, postoperative cardioversion should be avoided.

Regional and global left ventricular function during intra-aortic balloon counterpulsation in patients with acute myocardial infarction shock

We evaluated the improvement in hemodynamic and left ventricular (LV) function in 15 patients with acute myocardial infarction and cardiogenic shock, who were treated with intraaortic balloon counterpulsation (IABP). They were studied by flow-directed right heart catheterization and nuclear angiography. IABP decreased LV end-diastolic volume from 134 to 114 ml and LV end-systolic volume from 100 to 72 ml. LV stroke volume increased from 34 to 42 ml and cardiac output from 3.0 to 3.6 L/min. Global LV ejection fraction increased from 27.6% to 36.1%, and this was due to improvement in regional ejection fraction in ischemic areas. Pulmonary capillary wedge pressure and pulmonary blood volume decreased. Right ventricular ejection fraction also increased significantly. IABP improved LV function in acute myocardial infarction.