Left ventricular function during isometric hand grip and cold stress in normal subjects

Hemodynamic effects of isometric exercise in hypertrophic cardiomyopathy: comparison with normal subjects

BACKGROUND

We assessed the hemodynamic effects of isometric exercise by an ambulatory radionuclide monitoring device (VEST) that measured left ventricular function in patients who had hypertrophic cardiomyopathy (HCM), with and without significant left ventricular outflow-tract obstruction at rest, compared with control subjects.

METHODS AND RESULTS

We studied 10 patients with obstructive HCM, 25 patients with nonobstructive HCM, and 11 control subjects. During VEST monitoring, all patients gripped a dynamometer at 75% of maximal strength for up to 5 minutes. End-diastolic, end-systolic, and stroke volumes; cardiac output; and systemic vascular resistance were expressed as a percentage of baseline. The mean exercise duration was similar among the 3 groups. During handgrip, heart rate, systolic blood pressure, and cardiac output increased significantly and similarly in the 3 groups. There was a significant difference in the lung activity between obstructive and nonobstructive HCM patients and control subjects (P <.001), with a fall in control subjects and no change in HCM patients, irrespective of obstruction. Control subjects showed a decrease in end-systolic volume (P =.02) and an increase in ejection fraction (P =.003) and stroke volume (P =.009), whereas these parameters did not change in HCM patients, irrespective of obstruction. Systemic vascular resistance increased in obstructive (P =.02) and nonobstructive (P <.01) HCM patients but did not change in control subjects.

CONCLUSIONS

Isometric exercise causes an abnormal and similar adaptation to load changes in obstructive and nonobstructive HCM patients, as compared with control subjects.

Prolongation of left atrial augmentation after handgrip stress in coronary artery disease: observation using pulsed Doppler flowmetry

Although alterations in left ventricular diastolic filling dynamics have been observed during myocardial ischemia, few data exist regarding temporal changes in left ventricular filling during recovery. Therefore, the authors evaluated transmitral inflow pattern during and after handgrip exertion in coronary artery disease (CAD) by using Doppler echocardiography. The study population consisted of 18 normal (N) subjects and 47 patients with CAD. Of the CAD patients, 17 had coronary lesions associated with a limited area of underperfused myocardium (seven with good collateral circulation and 10 with distal lesions) (MILD), 15 patients exhibited a proximal lesion in a single vessel (SVD), and 15 patients had significant multivessel disease (MVD). Transmitral inflow velocities were continuously recorded at baseline, during handgrip exercise (50% of maximal for 1 minute), and for 5 minutes of recovery. Mean blood pressure, heart rate, early diastolic (E) and late atrial (A) inflow velocities, A/E ratio, and percent changes in E, A, and A/E from baseline were measured. In N and MILD, respectively, left ventricular inflow pattern returned to baseline at 3 minutes after handgrip (%E: 0.7 +/- 7.6%, 6.4 +/- 13.7%; %A: -0.2 +/- 7.9%, 3.1 +/- 6.5%; %A/E: -0.1 +/- 9.7%, -1.7 +/- 12.9%). In SVD and MVD, respectively, change in left ventricular inflow pattern was continued at 3 minutes after handgrip (%E: 7.2 +/- 9.4%, -4.3 +/- 17.2%, %A: 15.4 +/- 11.7%, 20.4 +/- 14.6%, %A/E: 7.9 +/- 10.0%, 29.2 +/- 25.6%). Increases in A and A/E in SVD and MVD were significantly higher than in N and MILD. Impaired left ventricular inflow pattern was observed at 3 minutes after handgrip in CAD, which may be reflected from prolonged impairment of diastolic function produced by ischemia. Therefore, temporal observation of left ventricular inflow pattern using the handgrip stress Doppler method may be useful for detection or follow-up of CAD.

Simultaneous assessment of function and perfusion during dipyridamole-handgrip Tc-99m sestamibi imaging in chronic coronary artery disease

The main goal of this work was to know the value of ventricular function in addition to perfusion Tc-99m sestamibi images in the assessment of coronary artery disease (CAD) when using dipyridamole (DIP) associated to isometric exercise. We analyzed 52 patients with suspected CAD; 40 of them had coronary lesions > or = 50% and 12 patients without CAD, conforming study and control groups, respectively. Twenty-eight patients had prior myocardial infarction. A two-day sestamibi protocol was employed with i.v. DIP-handgrip and rest injections, acquiring ECG-gated first pass and planar perfusion images. Sensitivity for perfusion images was 85% and specificity was 91.7%. There was no change between rest and DIP ejection fraction (EF) in controls. CAD patients presented a significant EF decrease with DIP (p: 0.0015). Patients with ischemia in perfusion images had larger EF decrease (p: 0.0001). For the analysis, an EF drop > or = 5% and any wall motion abnormality (WMA) were considered as having an abnormal response to DIP. CAD sensitivity improved significantly to 92.5% when adding EF drop and to 90% when adding WMA parameters, but specificity decreased to 75% with EF drop, and to 58.3% with WMA. In conclusion, first pass parameters from DIP-isometric exercise in addition to perfusion images are not a significant help in the assessment of CAD.

Usefulness of isometric hand grip exercise in detecting coronary artery disease during dobutamine atropine stress echocardiography in patients with either stable angina pectoris or another type of positive stress test

Dobutamine atropine stress echocardiography (DASE) detects coronary artery disease (CAD) by increasing myocardial oxygen demand causing ischemia. The sensitivity of the test for detection of CAD is reduced in patients with submaximal stress. We hypothesized that increasing cardiac work load by adding isometric exercise would improve the detection of ischemia during DASE. We studied 31 patients, mean age 57+/-11 years, with angiographically documented CAD. Patients underwent DASE using incremental dobutamine doses from 5 to 40 microg/kg/min, followed by atropine if peak heart rate was <85% of predicted maximal. Hand grip was then performed for 2 minutes at 33% of maximal voluntary contraction, while dobutamine infusion was maintained at the peak dose. The addition of hand grip during dobutamine stress was associated with a significant increase in systolic blood pressure (143+/-21 vs 164+/-24 mm Hg, p = 0.001) and left ventricular end-systolic circumferential wall stress (72+/-30 x 10(3) dynes/cm2 vs 132+/-34 x 10(3) dynes/cm2, p = 0.004). Wall motion score index increased from 1.0 at rest to 1.15+/-0.18 with dobutamine (p = 0.0004 vs rest), and increased further to 1.29+/-0.22 with the addition of hand grip (p = 0.004 vs dobutamine). Ischemia was detected in 19 patients (62%) with dobutamine-atropine stress alone and in 25 (83%) after the addition of hand grip (p <0.05). The addition of hand grip during DASE is feasible, and improves the detection of myocardial ischemia.

Exercise-induced aortic flow parameters in early postmenopausal women and middle-aged men

OBJECTIVE

Exercise Doppler echocardiography has been recognised as an accurate method for the assessment of left ventricular function in patients with coronary artery disease. Gender differences in aortic flow parameters during exercise have not been well established. The aims of this study were to compare basal ejection Doppler indexes in healthy early postmenopausal women with those of men, and to assess the effects of both isometric and dynamic exercises on these parameters.

DESIGN

Intergroup comparison between early postmenopausal women and middle-aged men.

SUBJECTS

Fifteen healthy women with a mean age of 55 (SD 5) years and 15 healthy men aged 52 (SD 4) were evaluated.

SETTING

Women were recruited from a menopause clinic and men from a primary cardiovascular prevention program at a cardiac rehabilitation institute.

INTERVENTIONS

Isometric exercise was performed with a 2-hand bar dynamometer, and dynamic exercise with a supine ergometer. Echo Doppler examination was performed at rest and at peak isometric and dynamic exercise with a pulsed Doppler transducer.

RESULTS

Both types of exercise resulted in higher values of hemodynamic parameters in the women, with most figures reaching statistical significance. Most aortic flow parameters during rest and exercise were also significantly higher in the women.

CONCLUSIONS

The unexpected higher values in hemodynamic and aortic flow parameters in early postmenopausal women as compared with middle aged men may shed light on a peculiar aspect of gender differences in cardiovascular function, perhaps specific to this age group and related to menopausal transition.

Cardiovascular response to sudden strenuous exercise: an exercise echocardiographic study

We studied the response in left ventricular (LV) internal dimensions and posterior wall thickness during the performance of sudden strenuous exercise without warm-up (SSE) and sudden strenuous exercise with warm-up (SSEw) in 15 healthy, untrained college-aged males (26 +/- 5.0 yr). Measurements of left ventricular end-diastolic dimension (LVEDD), left ventricular end-systolic dimension (LVESD), stroke dimension (SD = LVEDD-LVESD), fractional shortening (FS = SD/EDD) and posterior wall thickness (PWT) were obtained from continuous 2-D targeted on M-mode echocardiography. Continuous EKG and blood pressure were obtained at rest and during the final 10 s of SSE (30 s of upright leg cycle ergometry of 400 W at 80 rpm). SSEw was preceded by warm-up exercise (6 min of graded leg cycle exercise of 2-min stages initial load 30 W, increasing in 30-W increments at 60 rpm, followed immediately by SSE). Our findings revealed that there were no significant differences in the LV internal dimensions (LVEDD, LVESD, FS, PWT), HR max, RPP max, ECG, and MAP max between SSE and SSEw. Sudden strenuous exercise without warm-up is not associated with a reduced LV function. The results of this study are contradictory to previous findings that have suggested that SSE is associated with transient global left ventricular (LV) dysfunction.

Differential responses in left ventricular diastolic filling dynamics with isometric handgrip versus isotonic treadmill exertion

Although the hemodynamic responses to isotonic and isometric exercise are different, few data exist comparing the response to left ventricular (LV) diastolic filling dynamics with these two forms of exertion. Therefore we performed Doppler examination before and at the end of isotonic and isometric exercise in 20 normal volunteers to define the differential responses of LV filling to these two forms of exertion. Transmitral inflow velocity signals from the apical view and phonocardiography were recorded before and at the termination of treadmill exercise (TRD) to 11 METs and handgrip (HG) 50% maximal for 2 minutes). Mean blood pressure (mBP), heart rate (HR), early diastolic (E) and late atrial (A) inflow velocities, mean acceleration rate (ACC) of E wave, time velocity integral of inflow (Ti), and isovolumic relaxation time (IRT) from second heart sound to onset mitral inflow were measured. Absolute changes from baseline were significantly different for the two forms of exertion: TRD versus HG: BP = 11 +/- 9 versus 36 +/- 10 mm Hg, HR = 37 +/- 16 versus 16 +/- 9 beats/min, E = 11.6 +/- 11.3 versus -7.0 +/- 9.4 cm/sec, A = 29.9 +/- 14.5 versus 14 +/- 12 cm/sec, ACC = 164 +/- 151 versus -56 +/- 135 cm/sec2, Ti = 1.9 +/- 3.0 versus -1.7 +/- 1.7 cm, and IRT = -12 +/- 9 versus 9 +/- 10 msec, all p < 0.0001 except for A, p < 0.001). Isotonic treadmill exercise resulted in enhanced early diastolic filling manifested by increases in E and ACC and a decreased in IRT. Conversely, isometric handgrip exercise produced evidence of reduced early filling including decreased E and ACC and slightly increased IRT. Thus the response of LV filling dynamics recorded by Doppler differs for isotonic and isometric exertion and likely reflects the variable pressure and flow alterations induced by these two forms of exertion.

Continuous measurement of left ventricular performance during and after maximal isometric deadlift exercise

BACKGROUND

Isometric exercise produces a reflex increase in arterial blood pressure that is proportional to the intensity and mass of muscle used during contraction. Little is known about the transient effects of heavy weight lifting on left ventricular performance. In this study, we measured continuous changes in left ventricular performance during maximal large-muscle isometric exercise using the standing deadlift position.

METHODS AND RESULTS

Ten healthy young men performed serial deadlifts at 50% of maximal voluntary effort for 90 seconds and 100% of maximal effort for 30 seconds. Echocardiographic imaging (apical four-chamber view), arterial blood pressure (brachial artery catheter), and electrocardiographic monitoring were recorded throughout the deadlift and for 30 seconds of recovery. Aortic flow velocity was also monitored during a separate series of deadlifts. During 100% maximal deadlift, mean arterial pressure increased from 108 +/- 4 to 164 +/- 6 mm Hg. Left ventricular ejection fraction declined initially (from 57 +/- 2% to 49 +/- 3%) at 15 seconds into the lift and recovered (56 +/- 1%) due to significant increases in end-diastolic volume (104 +/- 11 ml to 132 +/- 16 ml) by the end of the lift. The peak systolic pressure/end-systolic volume ratio did not change during the deadlift. After cessation of the deadlift, mean arterial pressure declined precipitously (to 88 +/- 4 mm Hg) within 5 seconds and gradually returned to baseline after 30 seconds. Left ventricular performance indexes all increased significantly during the recovery phase (ejection fraction to 68 +/- 3%, peak systolic pressure/end-systolic volume ratio to 5.9 +/- 0.9). Findings were qualitatively similar for the 50% deadlift.

CONCLUSIONS

During an intense isometric deadlift, left ventricular performance declines initially but is restored by the Frank-Starling mechanism. Upon release of the deadlift, increased left ventricular performance develops in conjunction with a rapid decrease in arterial pressure. The combined effects of increased wall stress during the lift phase and enhanced contractility during the release phase probably contribute to left ventricular hypertrophy associated with repetitive weight training.

A survey of nuclear cardiological practice in Great Britain. The British Nuclear Cardiology Group

There is little information on the practice of nuclear cardiology in Great Britain. On behalf of the British Nuclear Cardiology Group in October 1988 we sent a postal questionnaire to 143 hospitals with nuclear medicine facilities (at least 70% of such hospitals). Sixty nine replies were received (48%), of which 23 (33%) were from teaching hospitals and 46 (39%) non-teaching. In these hospitals 147,904 isotope investigations were performed annually (mean 2311 per centre) of which 17,298 (12%) (mean 254 per centre) were cardiac studies. Of these, 59% were equilibrium radionuclide ventriculograms, 14% first pass ventriculograms, and 27% thallium-201 scans. Rest studies were performed more commonly by radiographers or technicians (63%) than by doctors (20%), but doctors were more commonly involved in stress studies (48%). Radiologists reported the studies more often (28%) than they performed them (6%). Methods of acquisition and analysis were varied and, for instance, the lower limit of normal left ventricular ejection fraction ranged from 35% to 75% (mean 49%). For thallium imaging 42% of centres used dipyridamole in some patients and 24% used tomography. These data show that nuclear cardiology techniques are used much less frequently in Great Britain than in countries such as the United States and Germany, that the ratio of blood pool to myocardial perfusion imaging is much higher than elsewhere, and that methods are poorly standardised. They may provide the impetus to improve the service and serve as a baseline for future surveys.

Impairment of left ventricular function during coronary angioplastic occlusion evaluated with a nonimaging scintillation probe

Impairment of left ventricular function during controlled myocardial ischemia induced by coronary angioplasty has been reported from angiographic and echocardiographic studies. Ejection fraction, peak ejection, peak filling rates, and end-systolic and end-diastolic volumes were investigated before, during and after coronary occlusion on-line with a nonimaging scintillation probe. The study consisted of 18 patients (mean age 59 +/- 10 years) with coronary artery stenosis of greater than 70%. During balloon inflation of 60 seconds' duration, coronary occlusion pressure was 31.6 +/- 12 mm Hg. There was no significant change in heart rate. Delay between first and second dilatation was 109 +/- 63 seconds. Ejection fraction decreased from 53 +/- 16 to 40 +/- 12% (first dilatation, p less than 0.01) and to 39 +/- 14% (second dilatation, p less than 0.01) and recovered to 51 +/- 16% 5 minutes after the second dilatation. Peak ejection rate was significantly reduced during the first and second balloon inflations. Peak filling rate decreased from 2.5 +/- 0.8 to 2.0 +/- 0.7 end-diastolic volume.s-1 (first dilatation, p less than 0.01) and to 1.8 +/- 0.7 end-diastolic volume.s-1 (second dilatation, p less than 0.01) and remained reduced at 2.2 +/- 0.7 end-diastolic volume.s-1 (p = not significant) at 5 minutes after the second dilatation. End-systolic and end-diastolic volumes increased significantly during the first and second dilatations and returned to normal after dilatation. It is concluded that short, controlled myocardial ischemia during coronary angioplasty leads to a decrease in systolic and diastolic left ventricular function. Sequential dilatations do not further decrease function if a sufficient interval is kept.

Physiology of exercise in the cold

Recreational and job requirements have increased the incidence in which humans exercise in cold environment. Understanding the physiological responses while exposed to cold entails knowledge of how exercise and cold interact on metabolic, cardiopulmonary, muscle and thermal aspects of human performance. Where possible, distinction are made between responses in cold air and cold water. While there is no consensus for diets most appropriate for working cold exposures, the evidence is strong that adequate amounts of carbohydrate are necessary. Carbohydrate loading appears to be efficacious, as it is for other athletic endeavours. Contrary to conventional wisdom, the combination of exercise and cold exposure does not act synergistically to enhance metabolism of fats. Free fatty acid (FFA) levels are not higher, and may be lower, with exercise in cold air or water when compared to corresponding warmer conditions. Glycerol, a good indicator of lipid mobilisation, is likewise reduced in the cold, suggesting impaired mobilisation from adipose tissue. Catecholamines, which promote lipolysis, are higher during exercise in cold air and water, indicating that the reduced lipid metabolism is not due to a lack of adequate hormonal stimulation. It is proposed that cold-induced vasoconstriction of peripheral adipose tissue may account, in part, for the decrease in lipid mobilisation. The respiratory exchange ratio (RER) is often similar for exercise conducted in warm and cold climates, suggesting FFA utilisation is equivalent between warm and cold exposures. The fractional portion of oxygen consumption (VO2) used for FFA combustion may decrease slightly during exercise in the cold. This decrease may be related to a relative decrease in oxygen delivery (i.e. muscle blood flow) or to impaired lipid mobilisation. Venous glucose is not substantially altered during exercise in the cold, but lactate levels are generally higher than with work in milder conditions. The time lag between production of lactate within the muscle and its release into the venous circulation may be increased by cold exposure. Minute ventilation is substantially increased upon initial exposure to cold, and a relative hyperventilation may persist throughout exercise. With prolonged exercise, though, ventilation may return to values comparable to exercise in warmer conditions. Exercise VO2 is generally higher in the cold, but the difference between warm and cold environments becomes less as workload increases. Increases in oxygen uptake may be due to persistence of shivering during exercise, to an increase in muscle tonus in the absence of overshivering, or to nonshivering thermogenesis. Heart rate is often, but not always, lower during exercise in the cold.(ABSTRACT TRUNCATED AT 400 WORDS)

Evaluation of preload reserve during isometric exercise testing in patients with old myocardial infarction: Doppler echocardiographic study

To estimate the preload reserve in response to an increase in afterload in patients with old myocardial infarction, the relation between the Doppler echocardiographic inflow velocity pattern and left ventricular end-diastolic pressure was investigated during isometric handgrip exercise testing. The study population consisted of 16 normal subjects and 40 patients with old myocardial infarction. The 40 patients were subdivided into two groups according to left ventricular end-diastolic pressure at rest: group I (22 patients), less than 18 mm Hg; group II (18 patients), 18 mm Hg or more. At rest, the ratio of peak velocity in atrial contraction phase to peak velocity in early diastolic filling phase (A/E) was significantly higher in the patients with old myocardial infarction than in normal subjects; values in the two subgroups of myocardial infarction did not differ significantly. The A/E ratio and left ventricular end-diastolic pressure increased significantly during exercise in group I. Conversely, the change in left ventricular end-diastolic pressure during exercise in group II was significantly greater than that in group I, and was associated with a decrease in the A/E ratio. Thus, an atrial compensatory mechanism operated effectively in response to the increase in afterload in patients with a normal left ventricular filling pressure, whereas this compensatory mechanism deteriorated in patients with elevated left ventricular filling pressure due to a limited preload reserve.

The ST segment of the ambulatory electrocardiogram in a normal population

The behaviour of the ST segment in everyday life was studied by ambulatory electrocardiography in 111 normal volunteers. Fifteen were excluded because of abnormal exercise responses (10 subjects) and significant postural ST segment shifts (five subjects). This left 62 men and 34 women, mean (SD) age 40.5 (12.6) years (range 20-67 years). Ambulatory monitoring of leads CM5 and CC5 for 24 hours was followed by a maximal treadmill exercise test. The tapes of the ambulatory monitoring were analysed by a computer aided system. The computer printed trend plots of the ST segment (measured both at the J point and at J + 60 ms) to detect episodes of ST segment elevation and depression, which were confirmed by visual analysis of real time printouts. Twelve subjects showed "ischaemic" ST segment depression and nine subjects showed ST segment elevation. Eight people with ambulatory ST segment changes were studied during exercise by radionuclide ventriculography and thallium-201 imaging scans. Although seven of the eight thallium studies were normal, radionuclide ventriculography showed functional impairment in five cases. Seven of the 10 subjects with abnormal exercise tests were similarly investigated and their results followed the same pattern, with normal thallium images in six and functional impairment in four. Ambulatory electrocardiography was repeated in 20 people after a median of 20 days. The ST segment changes were reproducible. ST segment changes of an apparently ischaemic nature occur even in a carefully defined normal population but they do not necessarily represent latent clinically significant coronary artery disease. This indicates that ST segment changes seen in patients with known obstructive coronary artery disease should be interpreted with caution.

Blood pressure behaviour during physical activity

Aerobic exercise is currently being recommended in addition to pharmacological therapy for lowering blood pressure levels in hypertensive patients, i.e. in subjects whose resting blood pressure levels exceed 145/90 mm Hg. On the other hand competitive sports are generally contraindicated in hypertensives, who are thought to be at increased risk of morbidity or mortality from their blood pressure levels. The present knowledge of blood pressure behaviour during isotonic physical activity is almost wholly based on the results obtained by means of the ergometric tests. Several maximal and submaximal exercise protocols have been introduced, but none has proved to be superior for diagnostic purposes. There is general agreement that the systolic blood pressure increase determined by isotonic exercise usually ranges from 50 to 70 mm Hg in both normotensive or hypertensive subjects. Diastolic blood pressure shows only minor changes in the normotensives, while in the hypertensives it tends to substantially increase because of their inability to adequately reduce their peripheral resistance. This mechanism may also explain the delay shown by the hypertensives in reaching pre-exercise blood pressure values during the recovery. On average diastolic blood pressure increases to a greater extent during bicycle ergometry than during treadmill, while no differences in exertional systolic blood pressure have been observed between the 2 tests. The results of several studies indicate that the blood pressure response to isotonic exercise is a marker for detection of hypertension earlier in the course of the disease, while resting blood pressure is still normal. According to some authors it is also of value in predicting future hypertension in individuals with borderline pressure levels. There are no conclusive data on the effect of training on blood pressure response to exercise. The majority of the published studies report small exertional pressure reductions after conditioning, which would merely reflect the reduction in resting blood pressure. Vasodilation greatly influences the exercise-induced rise in blood pressure; in fact the exertional pressor increase is blunted when the test is preceded by an adequate warm-up session. Isometric effort is thought to be contraindicated in hypertensive subjects, as it causes a pronounced increase not only of systolic but also of diastolic pressure. Mean blood pressure is, however, increased to the same extent by isotonic and isometric exercise, even though minor discrepancies have been reported by some authors.(ABSTRACT TRUNCATED AT 400 WORDS)