Physiological effects of short-term training after myocardial infarction.

The effects of a period of 4 weeks training on treadmill exercise performance were evaluated in 27 patients, mean +/- SD age 55 +/- 7 years, who had previously suffered a myocardial infarction (17 Q-wave) 3-24 months (mean 11 +/- 8). To ensure comparability of exercise levels only patients who obtained their predicted maximal heart rate in the initial test were included. All trained 3-4 hours daily 5 days a week at an average maximal intensity of 85% of their initial peak heart rate. They performed 2 maximal exercise tests before and 1 after the training course. Maximal oxygen consumption was 28.1 +/- 5.3 and 28.8 +/- 6.5 ml/kg/minute (NS) before, and increased by 16% to 33.4 +/- 7.2 after training (P less than 0.01). Treadmill exercise distance was 510 +/- 153 and 559 +/- 163 meters (10% increase, P less than 0.01) before, and increased by 14% to 638 +/- 156 after (P less than 0.01). Heart rate, ratio of respiratory gas exchange, and breathing frequency remained unchanged in all three tests at maximal exercise, but were significantly lower at identical submaximal levels after training, while the respiratory tidal volume increased. Resting heart rate decreased by 12% after (P less than 0.01). Thus, aerobic exercise performance is improved by short-term training after myocardial infarction. By the longitudinal design of the study, and the maximal initial exercise test, this physiological improvement can be differentiated from that of increased motivation, and of increased treadmill exercise distance due to improved exercise technique.

Effects of impaired lung function and pulmonary regurgitation on maximal exercise capacity in patients with repaired tetralogy of Fallot.

Long-term haemodynamic results and exercise capacity were studied in 34 patients with tetralogy of Fallot (24 men and 10 women) repaired 10.0 +/- 4.9 (mean +/- SD) years previously and compared to 34 healthy matched controls. All subjects were studied by resting spirometry, echocardiography and a symptom limited treadmill exercise test (modified Bruce protocol). The maximal oxygen consumption was 38.2 +/- 8.0 ml.kg-1.min-1 in patients and 48.1 +/- 8.1 ml.kg-1.min-1 in the control group (P < 0.001). Reduced maximal oxygen consumption was found in patients with low vital capacity (VC) and pulmonary regurgitation (PR). The ventilatory anaerobic threshold (VAT) was 23.8 +/- 0.6 ml.kg-1.min-1 and 29.9 +/- 0.6 ml.kg-1.min-1 in patients and controls, respectively (P < 0.001). VC was 3.4 +/- 1.21 in patients and 4.0 +/- 1.31 in controls (P < 0.02). In the patients, maximal ventilation was reduced and at submaximal exercise, the breathing frequency increased. Heart rates during exercise were similar in patients and controls. Tricuspid regurgitation (TR) was detected in 20 patients (58.8%); however, the exercise capacity was not reduced. Thus, impaired exercise capacity in tetralogy of Fallot is partly due to reduced resting lung function, pulmonary regurgitation and low ventilatory anaerobic threshold.

[Improved aerobic exercise performance after short-term training of patients with coronary disease]. / Okning av aerob arbeidskapasitet ved kortvarig trening av hjertepasienter.

Maximal oxygen consumption was measured during treadmill exercise in 44 patients with coronary artery disease. Exercise was performed before and after a 4-week course of training. Patients with a previous myocardial infarction and no angina pectoris (n = 27) increased their maximal oxygen consumption by 16% after training. There was no such increase in patients with angina pectoris (n = 17). The subjective feeling of wellbeing after training was the same in both groups of patients. Thus, the advantages of short term training can be both of a symptomatic character and a real improvement in cardiovascular function.

Arterial and venous measurement in resting forearm of metabolic indicators during rest and leg exercise.

We compared the levels of various metabolic indicators in arterial and venous forearm blood during maximal treadmill leg exercise, and the subsequent 9 min in nine volunteers aged 31-56 years. At maximal exercise plasma lactate was 13.2 +/- 3.1 mmol l-1 arterially, while venous was 41% lower, but increased more than arterial after exercise. There was a linear relationship between arterial and venous samples during and after exercise, but not at baseline. Plasma pyruvate increased on the arterial side from 49 +/- 8 to 172 +/- 30 mumol l-1 at maximal exercise, maximal venous was 21% lower. Free fatty acids were not different at rest, but decreased during exercise by 52 and 38% on the arterial and venous side. There was no relationship between arterial and venous levels. Changes in these three variables occurred significantly earlier on the arterial side. Arterial cyclic AMP rose from 97.3 +/- 28.4 to 262.7 +/- 67.5 nmol l-1 from rest to exercise, and was linearly inversely related to the decrease in free fatty acids. The mean venous pH was lower than arterial at rest, but was the same as arterial at maximal exercise and after. Thus, venous plasma lactate and pyruvate, but not free fatty acids, are linearly related to arterial measurements during maximal exercise, while pH is identical. Non-working muscle modifies exercise-induced changes, and therefore venous and arterial forearm blood sampling give more information than either alone.

Addition of sodium to the nonionic contrast medium iohexol during coronary angiography in man. Lack of electrocardiographic or hemodynamic effects.

It has recently been claimed that lack of sodium in nonionic contrast media may increase the risk of ventricular arrhythmias during coronary angiography. Thus, the influence of sodium addition to the nonionic contrast medium iohexol was studied in 75 patients with severe coronary heart disease. The study design was randomized, parallel and double-blind, and iohexol was given either with or without addition of NaCl (28 mmol/l). Both formulations induced a transient drop in arterial blood pressure, and prolongation of the QT interval and QRS duration at 10 s only (p less than 0.01). The electrical QRS axis was significantly changed by the coronary artery injections after 10 s, but not later. No differences between iohexol with and without NaCl were observed for any of the variables studied. No serious arrhythmias were observed. Thus, the addition of NaCl (28 mmol/l) to iohexol did not influence the electrocardiographic or hemodynamic changes induced by iohexol during coronary angiography.

Cardiovascular and electrocardiographic effects of iopentol in left ventricular angiography. Comparison of the low-osmolar, non-ionic iopentol (Imagopaque 350) and the hyper-osmolar, ionic metrizoate meglumine-Na-Ca (Isopaque Coronar 370) in patients with coronary heart disease.

UNLABELLED: The aim of the study was to evaluate and compare the hemodynamic and electrocardiographic effects following injection of the non-ionic, low-osmolar contrast medium iopentol (Imagopaque 350, Nycomed Imaging AS, Oslo, Norway) and the ionic, hyper-osmolar contrast medium metrizoate meglumine-Na-Ca (Isopaque Coronar 370, Nycomed Imaging AS, Oslo, Norway) when used for left ventricular angiography. The study was performed in a double-blind, randomized manner in 82 patients with severe coronary heart disease. The patients who received iopentol experienced less adverse events and subjective discomfort of lesser intensity than those who received metrizoate (p = 0.0001). Both contrast media induced a biphasic change in left ventricular (LV) systolic pressure, with an initial fall followed by a prolonged rise, but the alterations were statistically significantly more pronounced with metrizoate than with iopentol. The changes in LV end-diastolic pressure (p = 0.023), and LV negative dP/dt (p = 0.002) were significantly more pronounced with metrizoate than with iopentol. Cardiac output and heart rate increased more with metrizoate, while stroke volume was equally increased by both agents. A prolonged increase in the QT-interval, throughout the 10-min observation period, was seen only after injection of metrizoate (p = 0.0006 for comparison between contrast media). CONCLUSION: Iopentol was well tolerated and induced markedly less severe hemodynamic and electrocardiographic alterations than did metrizoate in patients with severe coronary heart disease.

Influence of low osmolality contrast media on electrophysiology and hemodynamics in coronary angiography: differences between an ionic (ioxaglate) and a nonionic (iohexol) agent.

It has recently been suggested that the addition of sodium to low osmolality contrast media may reduce the incidence of ventricular fibrillation and conduction disturbances during coronary angiography. In a randomized, double blind study of 30 patients undergoing coronary angiography we therefore examined the electrophysiological and hemodynamic effects of the two low osmolality contrast media-ioxaglate (with sodium) and iohexol (without sodium). Standard ECG, aortic blood pressure, and His bundle electrocardiogram were recorded. The contrast media were well tolerated and no serious arrhythmias were observed. Both induced a transient decrement in systolic blood pressure and reduction in heart rate 10 s following contrast injection (all P less than 0.01). Ioxaglate prolonged the QT interval at 10 s (P less than 0.01) and also when analysed for the whole observation period (120 s) (P less than 0.05), whereas iohexol did not cause any significant changes in the QT-interval. The AH-interval was prolonged by ioxaglate at 10 s (P less than 0.01), but not altered by iohexol. Thus, other factors than osmolality and sodium content might contribute to QT prolongation, since only the contrast agents with sodium (ioxaglate) induced QT prolongation in this study.