Comparison of two calcium blockers on hemodynamics, left ventricular mass, and coronary vasodilatory in advanced hypertension.

Dihydropyridine and nondihydropyridine calcium channel blockers (CCB) differ in pharmacologic characteristics. Few clinical studies distinguish effects of CCB as monotherapy. We conducted a comprehensive comparison of two CCB on patients with moderate to severe hypertension. Thirty patients with pretreatment diastolic blood pressures > or = 100 mm Hg were randomly assigned to either nifedipine-GITS or verapamil-SR. Dose titration achieved a diastolic blood pressure of < or = 95 mm Hg or a decrease of > or = 15 mm Hg over 4 weeks. Clinic blood pressure (BP), 24-h ambulatory BP, exercise BP, left ventricular mass, systolic and diastolic function by echocardiography, and coronary flow reserve by split-dose thallium-201 imaging with adenosine were assessed at baseline, end of titration, 3 months and 6 months of treatment. Plasma renin activity, atrial natriuretic peptide, norepinephrine, and epinephrine were assayed. Both drugs caused similar reductions in clinic and 24-h ambulatory BP and similar reductions in left ventricular mass index. Compared to nifedipine-GITS, verapamil-SR produced a significantly lower resting and peak exercise heart rate. Nifedipine-GITS elicited a lower peak exercise systolic BP. At end titration nifedipine-GITS produced lower plasma atrial natriuretic peptide levels, no longer apparent by 6 months. Plasma norepinephrine was lower with verapamil-SR, also at end titration and at 3 months, but not at 6 months. Plasma epinephrine and plasma renin activity were unchanged by either drug. There was no difference for systolic or diastolic left ventricular function or coronary flow reserve between the two treatments. Once daily nifedipine-GITS and verapamil-SR are equally effective for reduction of arterial pressure in moderate to severe hypertension. Differences in their hemodynamic profiles and neurohormonal responses are consistent with preclinical pharmacologic characteristics. The clinical implications of their similarities and differences remain to be fully evaluated in outcome studies.

Effects of fire fighting uniform (modern, modified modern, and traditional) design changes on exercise duration in New York City Firefighters.

Fire departments have replaced traditional uniforms with modern, more thermal protective gear. Although the new uniforms afford superior burn protection, they may reduce work time. Our purpose was to determine if exercise time was (1) reduced by wearing the modern versus traditional uniform, and (2) increased by a design change to a modified modern uniform (T-shirt and short pants rather than a shirt and long pants under the outer uniform). Male firefighters (n = 23; age 27 to 59) performed a maximum exercise test in gym clothes (maximal oxygen consumption = 46 +/- 9 ml/kg/min) and then returned on separate days to exercise using a moderately high intensity, constant work rate treadmill protocol while wearing fire fighting breathing apparatus and each of three uniforms. Firefighters exceeded anaerobic threshold by 1 minute and eventually reached or exceeded maximum heart rate and maximal oxygen consumption. Exercise time in modern (15 +/- 3 min) was significantly less than in traditional (18 +/- 5 min) uniform. Exercise time in modified modern (17 +/- 5 min) was significantly greater than in modern and not significantly different than in traditional uniforms. The rate of change in oxygen consumption and water loss were significantly affected by uniform type, with faster rates in modern compared with modified modern or traditional uniforms. These findings show the impact that design changes have on energy demands and exercise duration.

Exercise-induced ventricular tachycardia associated with coronary arteriovenous fistula and correction by transcatheter coil embolization.

Exercise-induced ventricular tachycardia is a well-described arrhythmia most commonly associated with atherosclerotic coronary artery disease. The case reported here presents its association with a coronary arteriovenous fistula, which has not been previously reported in the literature.

Resting diastolic function and left ventricular mass are related to exercise capacity in hypertensive men but not in women.

We evaluated the impact of diastolic function and gender on exercise capacity in sedentary, untreated hypertensive subjects (34 men, 23 women) using echocardiography and a bicycle ergometry with measurement of oxygen consumption (VO2). In men, peak (A) mitral inflow velocity and left ventricular (LV) mass were inversely related to peak VO2 (r = -0.64) and maximal workload (r = -0.57) and were the sole independent determinants of exercise capacity. In women, there was no relationship between any echocardiographic measure and exercise capacity. Thus, LV mass and Doppler-determined diastolic function predict maximal VO2 in hypertensive men but not in women. This finding may be related to gender differences in the contribution of diastolic filling to exercise capacity or may reflect limitations of resting Doppler echocardiography to predict exercise diastolic filling in hypertensive women.

Effects of blood donation on exercise performance in competitive cyclists.

This study evaluated 10 male cyclists before and after phlebotomy to determine the effect of donation of 1 U of blood on exercise performance. Each subject underwent maximal exercise testing with oxygen consumption measurement at baseline, 2 hours after phlebotomy, 2 days after phlebotomy, and 7 days after phlebotomy. Maximal performance was decreased for at least 1 week. Submaximal performance was unaffected by blood donation.

Hemodynamic compromise secondary to a mediastinal bronchogenic cyst.

Bronchogenic cysts are not commonly the cause of severe symptoms, and often present only as an abnormality on chest roentgenogram. We report an unusual patient with a mediastinal bronchogenic cyst associated with rapid hemodynamic deterioration secondary to compression of vital structures.

Effect of athletic training on heart rate variability.

The time and frequency domain components of heart rate variability have been used to assess prognosis in patients with different types of heart disease. However, the effect of habitual exercise, which influences baseline parasympathetic tone, on heart rate variability has not been fully evaluated. To determine the effect of chronic exercise on heart rate variability, we studied 12 athletes and 18 control subjects. Time domain and frequency domain analysis was performed on 15-minute resting heart rate acquisitions. Athletes had evidence of increased vagal activity in the time domain compared with control subjects (eg, increased standard deviation of R-R intervals) but showed evidence of decreased power in variables reflecting vagal activity in the frequency domain (eg, total power and high-frequency power). Of note, there was good correlation between time and frequency domain variables, which reflected parasympathetic tone in the control group that was not seen in athletes. These data suggest that frequency domain analysis of heart rate variability may not be an accurate indicator of cardiac vagal tone in chronically trained endurance athletes and activity level may have to be considered when using heart rate variability to carry out prognostic stratification in patients with heart disease.

Predictive accuracy of criteria used to assess maximal oxygen consumption.

To evaluate criteria frequently used to designate an exercise test as maximal, 33 men and 18 women completed progressive incremental cycle ergometry to exhaustion with direct measurement of oxygen consumption (VO2). On a separate day, subjects exercised at 115% of the maximal work rate attained in the first test following a 5-minute warm-up. If VO2 exceeded that of the progressive test by greater than or equal to 150 ml/min, subjects returned on a third day and pedalled at 125% of the first day's work ratepeak. This procedure was repeated until VO2 increased less than 150 ml/min, and defined whether the progressive test was a maximal or nonmaximal test. There were 45 tests that met the criterion for maximum during the progressive test and six nonmaximal tests. Respiratory exchange ratio and 85% age-predicted maximal heart rate were sensitive criteria for a maximal test but were not specific. Attainment of age-predicted maximal heart rate and peak lactate greater than 8 mmol/L were highly specific but insensitive measures of a maximal test. In the absence of a VO2 plateau, age-predicted maximal heart rate and lactate greater than 8 mmol/L can be used as indicators of maximal tests with a high degree of confidence. When age-predicted maximal heart rate or lactate greater than 8 mmol/L are not attained, the test may still be maximal because negative predictive value is low.

Exercise-related atrioventricular block. Influence of myocardial ischemia.

A 62-year-old woman was noted to have complete heart block immediately following an exercise stress test. Coronary arteriography subsequently revealed a significant lesion in the right coronary artery, which was successfully dilated. Thallium-exercise testing following angioplasty showed no evidence of inducible ischemia and no arrhythmia was seen, supporting the idea that exercise-related heart block may occur secondary to myocardial ischemia.