Evaluation of left ventricular performance in coronary heart disease: use of isometric handgrip stress test

Overview of stress echocardiography: uses, advantages, and limitations

Responses of the heart to changes in our environment are probably even more important than how the heart functions at rest. Accordingly, stress testing with noninvasive imaging has become important for diagnosis, prognosis, and monitoring the effects of therapy. Echocardiography at rest and with stress permits characterization of global and segmental left ventricular function as well as valvular structure and function. Moreover, echocardiography can be performed during or after a number of different physical or even mental stressors. Advantages of stress echocardiography include its ready availability, relatively low capital cost, and incremental value in that it allows characterization of cardiac anatomy as well as the myocardial response to a potentially ischemic stimulus. Moreover, echocardiography has the potential to image myocardial perfusion along with wall motion and wall thickening. Substantial literature has now been accumulated on the value of stress echocardiography for the diagnosis of ischemic disease, preoperative risk assessment, and assessment of myocardial viability. Echocardiography has compared generally well with nuclear imaging techniques for the detection of angiographic coronary artery disease. Overall sensitivity, however, has been slightly less, particularly for the detection of single-vessel coronary disease, although specificity has been on average somewhat higher than nuclear cardiology techniques. Because of the potential for variability in study acquisition as well as interpretation, careful safeguards need to be employed. Specifically, meticulous technique needs to be applied to obtain high-quality images and to assure that those images are obtained promptly after treadmill exercise stress. Only readers with specific interest and expertise should interpret stress echocardiography studies. Continuing efforts need to be made to assess and minimize variability and to assure continuing quality improvement. Advances in instrumentation, including evolving technology for real-time 3-dimensional imaging, and echocardiography contrast assessment of myocardial perfusion will likely improve the sensitivity of echocardiography and further extend its usefulness.

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.

Evaluation of coronary artery disease in the patient unable to exercise: alternatives to exercise stress testing

Exercise stress testing is a well-established method for the diagnostic, prognostic, and functional assessment of patients with known or suspected CAD. A variety of alternative tests have been described in patients unable to perform leg exercise. Atrial pacing and dipyridamole imaging have been evaluated most extensively, and results compare favorably with those of exercise testing for diagnosing the presence of CAD. Both tests may be used to assess prognosis after myocardial infarction, and dipyridamole imaging may be useful in patients undergoing preoperative evaluation. The use of the cold pressor test and isometric handgrip exercise have also been described. However, the value of both tests is limited by a relatively low sensitivity for detecting the presence of CAD. Other testing modalities--arm ergometry, intravenous infusion of beta-adrenergic agonists, and transthoracic pacing--show promise but require further assessment to confirm their value.

Effect of coronary artery bypass grafting on left ventricular response to isometric exercise

The left ventricular (LV) response to isometric exercise was evaluated in 20 patients who performed handgrip exercise tests before and 3 months after coronary artery bypass grafting. Preoperative LV ejection fraction (EF) decreased during the handgrip test from 0.57 +/- 0.08 to 0.49 +/- 0.09 (p less than 0.001); the ratio between the LV peak systolic pressure (PSP) and end-systolic volume index (ESVI) did not change. In 12 patients with patent grafts, the LVEF after operation did not change (0.54 +/- 0.06 at rest and 0.56 +/- 0.06 during handgrip exercise) and PSP/ESVI ratio increased from 4.5 +/- 1.5 to 5.6 +/- 2.1 mm Hg/ml X m-2 (p less than 0.001) during exercise. In 8 patients with occluded grafts, the LVEF after operation decreased from 0.56 +/- 0.10 to 0.48 +/- 0.06 (p less than 0.02), whereas PSP/ESVI did not change during handgrip exercise. Thus, the LV response to isometric handgrip exercise appears to improve after coronary artery bypass grafting in patients with patent grafts, but not in patients with 1 or more occluded grafts.

Insensitivity of the cold pressor stimulation test for the diagnosis of coronary artery disease

Cold pressor stimulation (CPS) was compared with supine bicycle exercise during radionuclide ventriculography as a procedure for diagnosing coronary artery disease (CAD). Thirty patients were studied. In the 18 patients with angiographically proved CAD, left ventricular ejection fraction (LVEF) decreased a mean of 5.0 +/- 1.0 ejection fraction units (+/- SEM) in response to CPS. Only two patients developed a new wall motion abnormality. In response to maximal supine exercise, the CAD group showed a mean decrease in LVEF from rest of 1.9 +/- 1.1%. Nine patients developed an exercise-induced wall motion abnormality. In the 12 patients with angiographically proved normal coronary arteries, LVEF decreased a mean of 5.8 +/- 1.3 units in response to CPS and increased a mean of 9.2 +/- 1.2% in response to exercise. Thus, the LVEF response to CPS was not significantly different in the CAD and normal groups (5.0 +/- 1.0 vs 5.8 +/- 1.3, NS). These same patients demonstrated the expected difference in LVEF response to exercise. We conclude that CPS produces similar changes in LVEF in patients with and without CAD, and therefore is not useful in diagnosing ischemic heart disease.

The relationship between left ventricular functional response to isometric exercise and asynergic contraction and diastolic stiffness

Either augmentation or impairment of left ventricular function has previously been reported in different patients, in response to isometric exercise. To identify the mechanisms associated with these disparate responses, the effects of submaximal sustained handgrip upon left ventricular systolic and diastolic properties were studied in 29 patients during diagnostic catheterization. In 16 patients (group I), ejection fraction, mean Vcf, and the mean systolic ejection rate remained constant, while the ratio of peak systolic pressure to end systolic volume increased significantly from 2.81 +/- 0.6 to 3.17 +/- 0.6 ml/mm Hg. In 13 patients (group II) ejection fraction declined from 0.6 +/- 0.03 to 0.51 +/- 0.03, Vcf from 0.96 +/- 0.09 to 0.85 +/- 0.09 circ/sec, mean normalized systolic ejection rate from 1.79 +/- 0.1 to 1.50 +/- 0.09 sec-1, and the peak systolic pressure to end systolic volume ratio from 2.23 +/- 0.3 to 1.99 +/- 0.3 (p less than 0.05 for each). Systemic arterial mean pressure increased similarly by 19% and 21% in groups I and II, respectively (p less than 0.05 for each). Systemic vascular resistance increased significantly by 23% in group I and by 5% in group II (p less than 0.05). Left ventricular end diastolic volume declined from 85.4 +/- 7 to 77.3 +/- 11 ml/m2 in group I, while end diastolic and end systolic volumes increased by 13% and 35%, respectively in group II (p less than 0.05 for each). In both groups, baseline exponential pressure-volume relations were similar, though higher intercepts on the pressure-volume relations upon the Y-axis suggested greater "diastolic tone," and steeper volume-normalized pressure-volume elasticity relations indicated "stiffer" left ventricular chambers in group II patients. While the incidence of coronary artery disease was similar, both the severity and extent of left ventricular asynergy were greater in group II patients. We conclude that dilatation and deterioration of left ventricular ejection function in response to isometric exercise are causally related to, and comprise a useful predictor of, severe underlying left ventricular asynergy and impaired chamber distensibility.

Response of the left ventricle to stress: effects of exercise, atrial pacing, afterload stress and drugs

A variety of tests are being utilized today to diagnose the presence of ischemic heart disease, assess the prognosis of myocardial and valvular heart disease and evaluate the effects of various pharmacologic agents on cardiac performance. This review summarizes the current evidence regarding the response of left ventricular performance and size to atrial pacing, afterload stress and various forms of exercise. The responses in normal persons and in subjects with coronary heart disease is reviewed and, when applicable, the effects of various pharmacologic agents on exercise performance in these patient groups are examined.