Scintigraphic study of relation between left ventricular peak systolic pressure and end-systolic volume in patients with coronary artery disease and normal subjects

Operative contractility: A functional concept of the inotropic state

1. Initial unsuccessful attempts to evaluate ventricular function in terms of the 'heart as a pump' led to focusing on the 'heart as a muscle' and to the concept of myocardial contractility. However, no clinically ideal index exists to assess the contractile state. The aim of the present study was to develop a mathematical model to assess cardiac contractility. 2. A tri-axial system was conceived for preload (PL), afterload (AL) and contractility, where stroke volume (SV) was represented as the volume of the tetrahedron. Based on this model, 'operative' contractility ('OperCon') was calculated from the readily measured values of PL, AL and SV. The model was tested retrospectively under a variety of different experimental and clinical conditions, in 71 studies in humans and 29 studies in dogs. A prospective echocardiographic study was performed in 143 consecutive subjects to evaluate the ability of the model to assess contractility when SV and PL were measured volumetrically (mL) or dimensionally (cm). 3. With inotropic interventions, OperCon changes were comparable to those of ejection fraction (EF), velocity of shortening (Vcf) and dP/dt-max. Only with positive inotropic interventions did elastance (Ees) show significantly larger changes. With load manipulations, OperCon showed significantly smaller changes than EF and Ees and comparable changes to Vcf and dP/dt-max. Values of OperCon were similar when AL was represented by systolic blood pressure or wall stress and when volumetric or dimensional values were used. 4. Operative contractility is a reliable, simple and versatile method to assess cardiac contractility.

Clinical and histologic features of alcohol drinkers with congestive heart failure

To clarify the difference between alcoholic cardiomyopathy and dilated cardiomyopathy and to investigate the characteristics of alcoholic cardiomyopathy, right ventricular endomyocardial biopsy was performed, and the two diseases were compared clinically and histologically. Changes in the cardiothoracic ratio, cardiac index, and systolic blood pressure/end-systolic volume index were greater after treatment in patients with alcoholic cardiomyopathy than in patients with dilated cardiomyopathy. Histologically, myocytic hypertrophy, fibrosis, and nuclear change were less significant in the former than in the latter. Among patients with alcoholic cardiomyopathy, the cardiac index in those with less fibrosis was greater than in those with more fibrosis. Thus patients with alcoholic cardiomyopathy had more preserved and reversible cardiac function and fewer histologic changes than the patients with dilated cardiomyopathy. Reversibility of cardiac function in patients with alcoholic cardiomyopathy correlated inversely with the severity of histologic changes.

Measurement of left ventricular contractility using transesophageal echocardiography in patients undergoing coronary artery bypass grafting. The Study of Perioperative Ischemia (SPI) Research Group

Optimal assessment of left ventricular function requires the use of load-independent indices of myocardial contractility, which often are difficult to obtain in patients undergoing coronary artery bypass graft (CABG) surgery. We have investigated whether the relation between left ventricular end-systolic stress (ESS) (derived from high-fidelity intraventricular pressure measurements and transesophageal-derived wall thickness) and end-systolic area (ESA) (derived from transesophageal echocardiography [TEE]) could provide a load-independent index of left ventricular function. We studied seven men undergoing coronary revascularization. Multiple data points at varied loading conditions were generated for each patient by infusions of sodium nitroprusside and phenylephrine during the period immediately after induction of general anesthesia and preceding surgical incision. While peak systolic blood pressure was pharmacologically altered between 78 and 204 mm Hg, the correlations between ESS and ESA were excellent for all patients (range r = 0.90 to 0.99). Additionally, the slopes of these relations showed a close correlation to their respective baseline thermodilution cardiac indices (r = 0.85, p = 0.02). Appropriate shifts of the ESS/ESA relationships were documented during postextrasystolic potentiation. The authors conclude that the left ventricular ESS/ESA correlation, derived using TEE and intraventricular pressure measurements, may provide a load-independent index of left ventricular inotropic state in patients undergoing CABG surgery.

Techniques for assessing inotropic effects of drugs in patients with heart failure: application to the evaluation of nicardipine

Evaluation of new drugs for the treatment of patients with heart failure requires assessment of the inotropic effects of these agents. Use of traditional indexes of contractility has been limited by the confounding effects of load on these measures of contractile function, although they have yielded meaningful conclusions in some studies. Recently, the end-systolic pressure volume relation (ESPVR) has emerged as a relatively load-independent measure of contractility. Because it is difficult to construct the relation in the clinical setting, several approximations have been introduced, some of which have significant limitations. We have applied the ESPVR to the assessment of the inotropic effect of the new dihydropyridine calcium channel blocker, nicardipine, in 15 patients with heart failure caused by systolic dysfunction. We constructed left ventricular pressure-volume loops from micromanometer pressure and radionuclide volume and manipulated afterload with nitroprusside. In response to intravenous nicardipine, mean arterial pressure fell from 91 +/- 4 (mean +/- SEM) to 72 +/- 2 mm Hg, left ventricular end-diastolic pressure fell from 27 +/- 2 to 23 +/- 3 mm Hg, cardiac index increased from 1.7 +/- 0.1 to 2.4 +/- 0.1 L/min/m2, and left ventricular ejection fraction increased from 0.15 +/- 0.01 to 0.19 +/- 0.01 (all p less than 0.05). Heart rate did not change. A rightward shift of the ESPVR, indicating a negative inotropic effect of nicardipine, was observed in 12 of 14 patients (p less than 0.05). We conclude that nicardipine improves left ventricular pump performance despite its negative inotropic effect in patients with severe heart failure. The improvement in pump performance can be attributed to afterload reduction.

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.

Left ventricular performance during psychological stress

Left ventricular ejection fraction, systolic blood pressure and plasma norepinephrine were measured in six normotensive and six mildly hypertensive subjects during rest and psychological stress. Compared with rest, 8 of the 12 subjects developed significant (P less than 0.05) changes in ejection fraction (increase in 6, decrease in 2); 10 of 12 subjects developed significant elevations of plasma norepinephrine; and all developed significant increases in systolic blood pressure. When the stress effects were examined for the total group, as opposed to within subjects, there were significant increases in plasma norepinephrine (P less than 0.001) and systolic blood pressure (P less than 0.001) but, interestingly, mean ejection fraction and stroke volume remained unchanged, implying stress led to increased left ventricular contractility.

Beneficial effects of long-term diltiazem treatment in dilated cardiomyopathy

There is increasing evidence that chronic enhanced exogenous or endogenous catecholamine stimulation in patients with dilated cardiomyopathy may worsen hemodynamic status and prognosis. The cause of this deterioration may lie in myocellular calcium accumulation and microcirculatory disorders. In a prospective study, the calcium channel antagonist diltiazem was given to 22 patients with dilated cardiomyopathy (60 to 90 mg three times daily) in addition to conventional therapy of digitalis, diuretics and vasodilators. Twenty-five patients received the conventional therapy and served as historical controls. Eight additional patients who were not originally included in this control group received adjunctive diltiazem treatment after initially receiving conventional therapy alone. The three patient groups were similar in all hemodynamic and anamnestic features. Only patients with reduced myofibrillar volume fraction on myocardial biopsy were included in the trial, because they could be expected to show hemodynamic deterioration. The mean survival time was 29 months in the control group, whereas no patient in the diltiazem group died over a mean follow-up period of 15.4 months (p less than 0.001). Mean left ventricular ejection fraction increased from 0.34 to 0.44 (p less than 0.001) and New York Heart Association functional class improved significantly in the diltiazem group and during the diltiazem period in the crossover patients, but deteriorated in the control group. The results suggest that adjunctive diltiazem treatment in dilated cardiomyopathy has beneficial effects on mortality, hemodynamics and symptoms.

Detection of left ventricular ischemia during atrial pacing: simultaneous assessment by echocardiography and invasive hemodynamic measurements

The ability of cross-sectional echocardiography to detect myocardial ischemia induced by atrial pacing was assessed during cardiac catheterization in 11 patients with coronary arterial disease. Angina pectoris was precipitated in all patients with increase in left ventricular end-diastolic pressure after pacing by 5 +/- 6 (mean +/- standard deviation) mm Hg (P less than 0.01). Regional left ventricular dysfunction occurred during pacing in all patients as determined by quantitative echocardiographic assessment of wall motion. Simultaneously, systolic reduction in parasternal short-axis area decreased (from 42 +/- 13 to 28 +/- 9%, P less than 0.01) with concomitant decrease in ejection fraction as determined in the apical four-chamber view (from 49 +/- 5 to 40 +/- 8%, P less than 0.01). In conclusion, echocardiography may detect pacing-induced myocardial ischemia through detection of regional and global left ventricular dysfunction. Inadequate regional perfusion may be indicated by echocardiography even in patients without apparent evidence of ischemia as determined by invasive hemodynamic measurements.

Digitizing and signal averaging of left ventricular pressure signals using a dedicated radionuclide imaging system

A method for obtaining left ventricular (LV) volume curves, synchronized with average LV pressure (LVP) curves for calculation of LV contractility, is described. Multiple gated blood pool imaging was performed to calculate average LV volume curves. Simultaneously with this acquisition, LVPs and aortic pressures were measured by indwelling catheters and recorded on an FM tape recorder. These signals were fed to the computer as image information and averaged and processed by the software developed for this purpose. Pressure resolution of the calibrated images was 4 mmHg/pixel when provision was made for a maximum pressure of 200 mmHg. A good correlation (r = 0.99) was obtained between the calculated peak LVPs and mean peak LVPs read from the chart recorder. The regression equation was: digitized peak LVP = 1.04 x chart recording--5.11 mmHg and the standard error of the estimate was 2.9 mmHg. Similar results were obtained with the aortic pressure (AP) measurements (digitized AP = 0.94 x chart recording + 6.37 mmHg, the standard error of the estimate was 3.8 mmHg). The digitized data also allowed the construction of pressure-volume loops for interpretation of ventricular contractility.

Spontaneous hemodynamic improvement or stabilization and associated biopsy findings in patients with congestive cardiomyopathy

The hemodynamic courses of 56 patients with congestive cardiomyopathy (CCM) were investigated. Fourteen patients died within 24 months after diagnosis. The hemodynamic courses of the remaining 42 patients were investigated in subsequent examinations by determination of left ventricular ejection fraction (LVEF), mean pulmonary arterial pressure at maximal workload, and peak systolic pressure/end-systolic volume index. During the study interval of 32.2 +/- 20.0 months the conditions of 20 patients (48%) deteriorated, according to their hemodynamic status, and at least five of these died of terminal heart failure. Surprisingly, the conditions of 22 patients (52%) improved or stabilized. One of these died of leukemia. Seven patients in the latter group with initial LVEFs of 0.30 or less experienced an average increase from 0.22 to 0.51. Retrospectively consideration of age, alcohol intake, exercise capacity, and hemodynamic status were not helpful in predicting the course of the disease. In 38 patients endomyocardial biopsy samples could be obtained at the time of diagnosis. Reduced myofibril volume fraction (less than 60%) had prognostic significance for both hemodynamic deterioration and death (sensitivity 23/24 = 96%), while 14 of 15 patients whose conditions improved or stabilized had a myofibril volume fraction of 60% or more (specificity 14/15 or 93%, p less than .002). A relationship between hemodynamic status and the myofibril volume fraction could not be found. Individual patients with CCM differ significantly with respect to course of the disease. A distinct separation of the patients by means of morphologic criteria is possible. This makes it more likely that the pathogenesis of the disease is not unique.

Analysis of phase-angle histograms from equilibrium radionuclide studies: correlation with semiquantitative grading of wall motion

Quantitative wall motion assessment from gated radionuclide left ventriculograms using phase analysis was studied in 14 subjects (6 normal volunteers and 8 patients with previous acute myocardial infarction). The standard deviation and skewness of the phase-angle histograms were determined from both global and segmental left ventricular (LV) regions of interest (septal, apical and posterolateral). Studies were performed at rest, after administration of atropine and after combined administration of phenylephrine and atropine. Both the standard deviation and skewness showed significant correlations with semiquantitative wall motion scoring. From the global analyses, the highest correlations were found after atropine administration (r = 0.86, p less than 0.001 for standard deviation and r = 0.72, p less than 0.001 for skewness). Nevertheless, deterioration in global wall motion scores correlated poorly with directional changes in standard deviation (r = 0.06, difference not significant) or skewness (r = 0.33, p less than 0.05). No significant correlation between skewness or change in skewness and wall motion scores were found with the segmental analyses. The maximal correlation between segmental standard deviation and segmental wall motion grading was again noted after atropine administration (r = 0.68, p less than 0.001), but deterioration in grading did not correlate with similar deterioration of the standard deviation (r = -0.05, difference not significant). Based on 90% confidence limits for normal standard deviation and skewness, an abnormal standard deviation (greater than 14.5) identified 13 of 28 wall motion disorders (sensitivity 46%), whereas an abnormal skewness (greater than 1.4) identified 1 of 28 wall motion disorders (sensitivity 4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of relationship between myocardial contractile state and left ventricular function in patients with aortic regurgitation

We studied the relationship between myocardial contractile state and left ventricular functional response to exercise in 14 asymptomatic patients with isolated moderate-to-severe aortic regurgitation and six control subjects. The slope of the systolic blood pressure-left ventricular end-systolic volume (pressure-volume) relationship determined by radionuclide ventriculography during angiotensin infusion was used as an indirect measure of myocardial contractility and was compared with left ventricular ejection fraction at rest and during both isometric handgrip and dynamic bicycle exercise. The slope of the pressure-volume relationship was significantly lower in patients with aortic regurgitation than in the control subjects (1.75 +/- 0.57 vs 2.78 +/- 0.42, p less than 0.01). The slope correlated exponentially with resting ejection fraction and was linearly related to changes in left ventricular ejection fraction during both handgrip and bicycle exercise. In patients with aortic regurgitation, resting ejection fraction may overestimate myocardial function. The slope of the pressure-volume relationship measured during afterload stress and left ventricular ejection fraction response to exercise intervention more reliably reflect the degree of left ventricular dysfunction.

Natural history of chronic mitral insufficiency: relation of peak systolic pressure/end-systolic volume ratio to morbidity and mortality

The ratio of peak systolic pressure to end-systolic volume (PSP/ESV) is a measure of contractility that is relatively independent of loading conditions. To define the relation of this index to the natural history of chronic mitral insufficiency, follow-up studies were performed in 76 patients. All had isolated mitral insufficiency and were followed up for an average of 48 months. None underwent surgery. Cardiac volumes, ejection fraction and PSP/ESV ratio were calculated and Cox multiple regression analyses were performed to determine the relation of functional status, ejection fraction and PSP/ESV ratio to morbidity and mortality. Twenty-three patients died during follow-up; in 70% of those who died, the PSP/ESV ratio was reduced below the 20th percentile. However, as an independent predictor of mortality, this ratio was less sensitive (p greater than 0.05) than ejection fraction (p less than 0.01). Similarly, functional status change was predicted more accurately by ejection fraction (p less than 0.01) than by the PSP/ESV ratio (p greater than 0.05). Thus, although a decreased PSP/ESV ratio was associated with a higher mortality rate, other clinical and laboratory variables were superior to this index for determining morbidity and mortality in patients with isolated mitral insufficiency.

The systolic arterial pressure/end-systolic volume relationship in patients with severe left ventricular dysfunction

Performance of the intact left ventricle is well-defined by the end-systolic pressure/end-systolic volume relationship that appears independent of preload and afterload. To determine whether noninvasive measurements of this relationship could distinguish normal from abnormal subjects, we evaluated the relationship between arterial systolic pressure (determined by cuff sphygnomanometry) and radionuclide estimates of end-systolic volume in 12 normal subjects and 24 patients with severe left ventricular dysfunction. Data were acquired at rest, after atropine injection, and then during at least three increments of arterial pressure (average total increase approximately 45 mm Hg) using phenylephrine. The relationship between peak-systolic pressure (SP) and end-systolic volume (ESV) was found to be linear in all subjects (r greater than or equal to 0.91). The slope of this line was steeper in normal subjects than in myopathic patients (73 +/- 21.7 vs 20.8 +/- 8.7 mm Hg/volume unit/m2, P less than 0.001) and the zero pressure intercept also was greater (49.8 +/- 30 mm Hg vs 27.1 +/- 44.2 mm Hg, P less than 0.01). Similarly, resting ejection fraction (EF) was greater in the normals (0.71 +/- 0.88 vs 0.21 +/- 0.07% P less than 0.001) and end-diastolic volume (EDV) was smaller (4.14 +/- 0.88 vs 6.58 +/- 0.65 volume units, P less than 0.01). Systolic pressure/end-systolic volume relationship determined by these noninvasive methods was linear in both patients with severely reduced cardiac function and normal control subjects, clearly distinguishing normal from severely impaired left ventricles.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of ventricular emptying and filling indexes during acute increases in arterial pressure

Using equilibrium radionuclide angiography, an evaluation was made of the response of left ventricular ejection and filling rates at rest and during acute increases in afterload in 8 normal volunteer subjects and 10 patients with previous transmural myocardial infarctions. Using the postatropine point for comparison, normal patients increased ejection time and decreased peak ejection rate (-3.90 +/- 0.49 vol/s to -3.41 +/- 0.95 vol/s) and peak filling rate (3.94 +/- 0.88 vol/s to 3.51 +/- 0.38 vol/s). Infarct patients had similar responses, although all indexes were lower than the corresponding values in the normal subjects. At rest, the ratio of peak filling to emptying rate was similar in the normal subjects and the infarct patients (1.01 +/- 0.24 versus 0.99 +/- 0.25, respectively) and maintained that relationship after atropine (0.91 +/- 0.11 versus 0.81 +/- 0.21) and at the peak increase in arterial pressure (1.07 +/- 0.21 versus 1.02 +/- 0.32). The ratio of time to peak filling/time to peak emptying behaved in similar fashion regardless of the differences in the absolute values. In this study, left ventricular filling and emptying behaved in a similar fashion in response to the alteration in arterial pressure in normal subjects and in patients with previous myocardial infarctions.

Radionuclide evaluation of the systolic blood pressure/end-systolic volume relationship: response to pharmacologic agents in patients with coronary artery disease

To assess the response of the relationship between systolic blood pressure and end-systolic volume to pharmacologic agents with known cardiac effects, we studied 21 patients with known coronary heart disease by means of gated radionuclide angiograms during the infusion of phenylephrine. Each individual was studied during the infusion of phenylephrine twice, once as a control and the second time after the administration of either intravenous dobutamine, topical nitroglycerin ointment, or intravenous propranolol. Eight individuals received 10 micrograms/kg/min of dobutamine, which reduced resting cardiac volumes (p less than 0.01), raised ejection fraction (p less than 0.01), and shifted the slope (1.38 +/- 0.50 to 2.03 +/- 0.69, p less than 0.01) and pressure intercept received 2 inches of nitroglycerin ointment. Nitroglycerin increased ejection fraction (p less than 0.05) and reduced volumes (p less than 0.05) but did not alter either the slope (1.46 +/- 0.68 to 1.49 +/- 0.61, p = NS) or intercept (10.6 +/- 5.4 to 10.1 +/- 6.4 mm Hg, p = NS) of the relationship. Eight patients received 15 mg of intravenous propranolol. Propranolol reduced resting ejection fraction (p less than 0.05), increased volumes (p less than 0.05), and reduced both the slope (1.67 +/- 0.58 to 1.51 +/- 0.53, p less than 0.05) and the intercept (13.8 +/- 2.5 to 7.5 +/- 2.3 mm Hg, p less than 0.05) of the pressure-volume relationship. Thus the systolic blood pressure/end-systolic volume relationship can be assessed from radionuclide angiograms.