Beat-to-beat left ventricular performance in atrial fibrillation: radionuclide assessment with the computerized nuclear probe

Left Atrial Size and Function in a Canine Model of Chronic Atrial Fibrillation and Heart Failure

BACKGROUND

Our aim was to assess how atrial fibrillation (AF) induction, chronicity, and RR interval irregularity affect left atrial (LA) function and size in the setting of underlying heart failure (HF), and to determine whether AF effects can be mitigated by vagal nerve stimulation (VNS).

METHODS

HF was induced by 4-weeks of rapid ventricular pacing in 24 dogs. Subsequently, AF was induced and maintained by atrial pacing at 600 bpm. Dogs were randomized into control (n = 9) and VNS (n = 15) groups. In the VNS group, atrioventricular node fat pad stimulation (310 μs, 20 Hz, 3-7 mA) was delivered continuously for 6 months. LA volume and LA strain data were calculated from bi-weekly echocardiograms.

RESULTS

RR intervals decreased with HF in both groups (p = 0.001), and decreased further during AF in control group (p = 0.014), with a non-significant increase in the VNS group during AF. LA size increased with HF (p<0.0001), with no additional increase during AF. LA strain decreased with HF (p = 0.025) and further decreased after induction of AF (p = 0.0001). LA strain decreased less (p = 0.001) in the VNS than in the control group. Beat-by-beat analysis showed a curvilinear increase of LA strain with longer preceding RR interval, (r = 0.45, p <0.0001) with LA strain 1.1% higher (p = 0.02) in the VNS-treated animals, independent of preceding RR interval duration. The curvilinear relationship between ratio of preceding and pre-preceding RR intervals, and subsequent LA strain was weaker, (r = 0.28, p = 0.001). However, VNS-treated animals again had higher LA strain (by 2.2%, p = 0.002) independently of the ratio of preceding and pre-preceding RR intervals.

CONCLUSIONS

In the underlying presence of pacing-induced HF, AF decreased LA strain, with little impact on LA size. LA strain depends on the preceding RR interval duration.

Measuring left ventricular peak longitudinal systolic strain from a single beat in atrial fibrillation: validation of the index beat method

BACKGROUND

It is traditionally difficult to estimate left ventricular (LV) systolic function in atrial fibrillation (AF). The aim of this study was to validate the use of an index beat, the beat after the nearly equal preceding (RR1) and pre-preceding (RR2) intervals, for the measurement of LV peak longitudinal systolic strain (PLSS). The difference between RR1 and RR2 intervals of the index beat must be <60 msec. LV PLSS measured from the index beat (PLSSindex) was compared with LV PLSS measured from the conventional but time-consuming method of averaging multiple cardiac cycles (PLSSavg).

METHODS

Ninety-eight patients with persistent or permanent AF and resting ventricular rates ≤ 105 beats/min were prospectively included. LV PLSSindex and LV PLSSavg were obtained from two-dimensional speckle-tracking echocardiography.

RESULTS

LV PLSSindex had a highly significant correlation with LV PLSSavg (r = 0.970, P < .001). Bland-Altman analysis showed only small bias of 0.01%, and the 95% limits of agreement were +1.64% to -1.62%. Compared with those with lower risk scores of stroke indicated by CHADS(2) scores < 2 or CHA(2)DS(2)-VASc scores < 2, patients with higher risk scores of stroke indicated by CHADS(2) scores ≥ 2 or CHA(2)DS(2)-VASc scores ≥ 2 had lower PLSSavg and PLSSindex (P ≤ .012).

CONCLUSIONS

LV PLSSindex was a good alternative to LV PLSSavg in patients with AF. Use of the index beat to measure LV longitudinal systolic strain in patients with AF was as accurate as the time-consuming method of averaging multiple cardiac cycles.

Meta-analysis of the effectiveness and safety of catheter ablation of atrial fibrillation in patients with versus without left ventricular systolic dysfunction

Catheter ablation is a promising therapy for atrial fibrillation (AF), but its utility in patients with left ventricular systolic dysfunction (LVSD) is uncertain. The objectives of this study were to perform a systematic review and meta-analysis of randomized and observational studies comparing the rates of recurrent AF, atrial tachycardia (AT), and complications after AF catheter ablation in those with versus without LVSD and to summarize the impact of catheter ablation on the left ventricular ejection fraction. Seven observational studies and 1 randomized trial were included (total n = 1,851). Follow-up ranged from 6 to 27 months. In those with LVSD, 28% to 55% were free of AF or AT on follow-up after 1 AF catheter ablation, increasing to 64% to 96% after a mean of 1.4 procedures. The relative risk for recurrent AF or AT in those with versus without LVSD was 1.5 (95% confidence interval 1.2 to 1.8, p <0.001) after 1 procedure and 1.2 (95% confidence interval 0.9 to 1.5, p = 0.2) after multiple procedures. No difference in complications was observed in patients with (3.5%) versus without (2.5%) heart failure (p = 0.55). After catheter ablation, those with LVSD experienced a pooled absolute improvement in the left ventricular ejection fraction of 0.11 (95% confidence interval 0.07 to 0.14, p <0.001). In conclusion, patients with and without LVSD had similar risk for recurrent AF or AT after catheter ablation, but repeat procedures were required more often in those with LVSD. Significant improvements in left ventricular ejection fractions after ablation were observed in those with LVSD. Randomized trials are needed given the limitations of present data.

Three-dimensional echocardiography using single-heartbeat modality decreases variability in measuring left ventricular volumes and function in comparison to four-beat technique in atrial fibrillation

Background

Three dimensional echocardiography (3DE) approaches the accuracy of cardiac magnetic resonance in measuring left ventricular (LV) volumes and ejection fraction (EF). The multibeat modality in comparison to single-beat (SB) requires breath-hold technique and regular heart rhythm which could limit the use of this technique in patients with atrial fibrillation (AF) due to stitching artifact. The study aimed to investigate whether SB full volume 3DE acquisition reduces inter- and intraobserver variability in assessment of LV volumes and EF in comparison to four-beat (4B) ECG-gated full volume 3DE recording in patients with AF.

Methods

A total of 78 patients were included in this study. Fifty-five with sinus rhythm (group A) and 23 having AF (group B). 4B and SB 3DE was performed in all patients. LV volumes and EF was determined by these two modalities and inter- and intraobserver variability was analyzed.

Results

SB modality showed significantly lower inter- and intraobserver variability in group B in comparison to 4B when measuring LV volumes and EF, except for end-systolic volume (ESV) in intraobserver analysis. There were significant differences when calculating the LV volumes (p < 0.001) and EF (p < 0.05) with SB in comparison to 4B in group B.

Conclusion

Single-beat three-dimensional full volume acquisition seems to be superior to four-beat ECG-gated acquisition in measuring left ventricular volumes and ejection fraction in patients having atrial fibrillation. The variability is significantly lower both for ejection fraction and left ventricular volumes.

Interrater reliability of cardiac output measurements by transcutaneous Doppler ultrasound: implications for noninvasive hemodynamic monitoring in the ED

INTRODUCTION

Hemodynamic monitoring is an important aspect of caring for the critically ill patients boarding in the emergency department (ED). The purpose of this study is to investigate the interrater agreement of noninvasive cardiac output measurements using transcutaneous Doppler ultrasound technique.

METHODS

This is a prospective observational cohort study performed in a 32-bed adult ED of an academic tertiary center with approximately 65000 annual patient visits. Patients were enrolled after verbal consent over a 7-month period. The raters were ED personnel involved in patient care. Paired measurements of cardiac index (CI) and stroke volume index (SVI) were obtained from a transcutaneous Doppler ultrasound cardiac output monitor.

RESULTS

A convenience sample of 107 (50 women and 57 men) patients with a median age of 49 (32, 62) years was enrolled. One hundred two paired measurements were performed in 91 patients in whom adequate Doppler ultrasound signals were obtainable. The raters included 35 emergency medicine attending physicians, 31 emergency medicine residents, 80 medical students, 47 nurses, and 11 emergency medical technicians. Cardiac index range was 0.6 to 5.3 L/min per square meter, and SVI range was 7.7 to 63.0 mL/m(2). The correlation of CI measurements between 2 raters was good (r(2) = 0.87; 95% confidence interval, 0.86-1.00; P < .001). Likewise, SVI measurements between 2 raters also showed acceptable correlation (r(2) = 0.84; 95% confidence interval, 0.81-0.96; P < .001). Interrater reliability was strong for CI (kappa = 0.83 with 92.2% agreement) and SVI measurements (kappa = 0.72 with 88.2% agreement). Most patients had an interrater difference below 10% in CI and SVI measurements.

CONCLUSIONS

Emergency department personnel, regardless of their role in patient care, are able to obtain reliable cardiac output measurements in ED patients over a wide range of CI and SVI. Transcutaneous Doppler ultrasound technique may be an alternative to traditional invasive hemodynamic monitoring of critically ill patients presenting to the ED.

Refinement on single-beat determination of left ventricular systolic function in patients with atrial fibrillation

Single-beat determination of left ventricular systolic function at a beat with equal subsequent cardiac cycles has been proposed as an accurate method in atrial fibrillation. However, there has still been substantial variability between the values calculated from beats with equal subsequent cycles. Therefore, some refinement on the single-beat method is needed. In 100 patients with atrial fibrillation, Doppler aortic flow time-velocity integral was determined for at least 20 consecutive cardiac cycles. The values at beats with equal subsequent cardiac cycles were chosen and compared with the average values over all cardiac cycles. The values at beats with cycle lengths shorter than 500 milliseconds were usually far below the average values over all cardiac cycles. Bland-Altman agreement analysis revealed improved accuracy by gradually narrowing the range of the limits of agreement when 2 or 3 beats with equal subsequent cycles and cycle lengths longer than 500 milliseconds were used for evaluation.

Biplane assessment of left ventricular function during atrial fibrillation at beats with equal subsequent cycles

BACKGROUND

Prior study has demonstrated that the biplane single-beat method could be used to assess left ventricular function during atrial fibrillation at a beat with equal subsequent cycles. The study was to test whether we could improve the method by measuring a few beats with equal subsequent cycles and cycle-length limits.

METHODS

In 75 patients with atrial fibrillation, stroke volume and ejection fraction were determined from simultaneous biplane views of left ventricle for 20 beats using a matrix-array transducer and a biplane Simpson's rule. The influence of cycle lengths on the values of systolic parameters at beats with equal subsequent cycles was examined from the plot of normalized parameters (measured values/average values) against cycle lengths. The values of 1 to 3 beats with equal subsequent cycles and cycle-length limits were averaged and compared with the average values over 20 beats by Bland-Altman and mean percentage difference analysis. The variability of repeat measurements was evaluated in 10 patients.

RESULTS

The systolic parameters measured at beats with cycle lengths shorter than 500 ms were usually far below the average values. Agreement and mean percentage difference analysis revealed improved accuracy when 2 or 3 beats with cycle-length limits (>500 ms) were used for assessment. As the variability of averaging 2 or 3 beats is no greater than that of repeat measurements, both methods are equally good.

CONCLUSIONS

Accurate assessment of left ventricular systolic function in atrial fibrillation can be obtained by averaging 2 beats with equal subsequent cycles and cycle-length limits (>500 ms).

Simultaneous biplane single-beat assessment of left ventricular systolic function in patients with atrial fibrillation

Left ventricular systolic function was studied in 40 patients with atrial fibrillation using a matrix-array transducer, which enables 2 simultaneous orthogonal views to be obtained in a biplane mode. Bland-Altman analysis showed excellent correlation and agreement between the systolic parameters of a single beat with identical RR1 and RR2 intervals and the measured average value over all cardiac cycles.

Asymptomatic versus symptomatic persistent atrial fibrillation: clinical and noninvasive characteristics

OBJECTIVE

This prospective study was designed to investigate the differences between asymptomatic versus symptomatic arrhythmia as well as left ventricular dysfunction in a consecutive population of patients with persistent atrial fibrillation.

DESIGN

A total of 282 consecutive outpatients referred with persistent atrial fibrillation formed the study population. A structured medical history was obtained. A two-dimensional transthoracic echocardiography to assess the left ventricular function and a 24-h electrocardiogram (ECG) recording were performed. Irregularity of the heart rhythm was analysed with heart rate variability (HRV) in the time domain as well as maximum and minimum heart rate and the longest pause.

SETTING

Three university hospitals.

RESULTS

The mean age of the patients was 69 years and the mean duration of atrial fibrillation was 7 months. The prevalence of symptomatic patients was 68%, while 32% had no symptoms from atrial fibrillation, left ventricular dysfunction was observed in 20%. Asymptomatic subjects had more often lone atrial fibrillation than those with symptoms. Valvular heart disease was an independent predictor of symptoms while male gender, ischaemic heart disease and a high heart rate were independent predictors of impaired left ventricular function.

CONCLUSION

Valvular heart disease is related to symptoms in persistent atrial fibrillation. Ischaemic heart disease, male gender and a high heart rate are more common in patients with impaired left ventricular function. Compromised left ventricular function does, occur also in asymptomatic subjects underlining the importance of a careful investigation including echocardiography in all subjects with persistent atrial fibrillation.

Factors predicting success rate and recurrence of atrial fibrillation after first electrical cardioversion in patients with persistent atrial fibrillation

BACKGROUND

The recurrence rate of atrial fibrillation (AF) after elective cardioversion is high.

HYPOTHESIS

The study aimed to identify clinical predictors for successful electrical cardioversion and maintenance of sinus rhythm after a first electrical cardioversion in patients with persistent AF without concomitant antiarrhythmic drugs of class I and III.

METHODS

Consecutive outpatients (n = 166) with persistent AF for > 1 month, scheduled for elective cardioversion, were prospectively included in the study. A clinical investigation, echocardiographic assay, and Holter electrocardiogram (ECG) before and ECG 4 weeks after cardioversion, were performed in all patients.

RESULTS

The mean age of the patients was 68 years (range 45-83) and duration of AF was 5 (1-48) months. Sinus rhythm was established in 124 (75%) patients. In multivariate analysis, only duration of AF < 6 months (p < 0.04, odds ratio [OR] 2.2, 95% confidence interval [CI] 1.1 to 4.7) and patients weight (p < 0.03, OR 2.3, 95% CI 1.1 to 4.8 for weight < 80 kg) were identified as independent predictors of successful cardioversion. At 4 weeks after cardioversion, only 46 (37%) of 124 patients maintained sinus rhythm. Independent factors for maintenance of sinus rhythm, in multivariate analysis, were AF <3 months (p < 0.04, OR 2.5, 95% CI 1.1 to 5.6), treatment with beta blockers (p < 0.00001, OR 7.0, 95% CI 3.0 to 16.3) or verapamil/diltiazem (p < 0.04, OR 3.6, 95% CI 1.1 to 12.1), and right atrial dimension < 37 mm (p < 0.02, OR 5.9, 95% CI 1.4 to 25.4).

CONCLUSIONS

In patients with persistent AF, the patient's weight and the duration of AF are independent predictors for a successful cardioversion. Short duration of AF, treatment with beta blockers or verapamil/diltiazem, and right atrial area/dimension are independent predictors for maintenance of sinus rhythm.

Left ventricular beat to beat performance in atrial fibrillation: dependence on contractility, preload, and afterload

OBJECTIVE

To assess independent determinants of beat to beat variation in left ventricular performance during atrial fibrillation.

DESIGN

Prospective study.

SETTING

University hospital.

PATIENTS

Seven patients with chronic non-valvar atrial fibrillation.

INTERVENTIONS

Invasive and non-invasive haemodynamic variables were assessed using a non-imaging computerised nuclear probe, a balloon tipped flow directed catheter, and a non-invasive fingertip blood pressure measurement system linked to a personal computer.

MAIN OUTCOME MEASURES

Left ventricular ejection fraction, left ventricular volume, ventricular cycle length, pulmonary capillary wedge pressure, and measures of left ventricular afterload (end systolic pressure/stroke volume) and contractility (end systolic pressure/end systolic volume) were calculated on a beat to beat basis during 500 consecutive RR intervals. A statistical model of the beat to beat variation of the ejection fraction containing these variables was constructed by multiple regression analysis.

RESULTS

Positive independent relations with ejection fraction were found for preceding RR interval, contractility, and end diastolic volume, while inverse relations were found for afterload, preceding end systolic volume, and preceding contractility (all variables, p < 0. 0001). A relatively strong interaction was found between end diastolic volume and afterload, indicating that ejection fraction was relatively more enhanced by preload in the presence of low afterload.

CONCLUSIONS

The varying left ventricular systolic performance during atrial fibrillation is independently influenced by beat to beat variation in cycle length, preload, afterload, and contractility. Beat to beat variation in preload shows its effect on ventricular performance mainly in the presence of a low afterload.

Influence of heart rate on stroke volume variability in atrial fibrillation in patients with normal and impaired left ventricular function

Both resting tachycardia and irregular ventricular rhythm may contribute to impaired cardiac performance in atrial fibrillation (AF). This study assesses the relation between resting heart rate and beat-to-beat changes in left ventricular (LV) ejection and filling in patients with normal and impaired LV systolic function. Beat-to-beat variation in LV outflow and inflow velocity-time integral was measured using pulsed Doppler ultrasound in 39 patients with chronic AF and normal (n=22) or impaired (n=17) LV systolic function. Aortic velocity-time integral variability increased with mean heart rate (p=0.003) even though RR interval variability decreased (p <0.001). Aortic velocity-time integral was more sensitive to the duration of both the preceding (p <0.001) and prepreceding (p <0.001) RR intervals at higher heart rates. These relations were similar for patients with normal and impaired LV systolic function. The sensitivity of the filling velocity-time integral to RR interval variability also increased with heart rate (p <0.001). However, at higher heart rates the filling velocity-time integral (p=0.009) and filling time (p=0.005) were less sensitive to change in RR intervals in patients with impaired LV function. We conclude that beat-to-beat stroke volume variability in AF increases with heart rate. Stroke volume variability was not influenced by LV systolic function.

Left ventricular beat-to-beat performance in atrial fibrillation: contribution of Frank-Starling mechanism after short rather than long RR intervals

OBJECTIVES

This study sought to evaluate control mechanism of the varying left ventricular performance in atrial fibrillation.

BACKGROUND

Atrial fibrillation is characterized by a randomly irregular ventricular response, resulting in continuous variation in left ventricular beat-to-beat mechanical behavior and hemodynamic variables.

METHODS

Fourteen patients with chronic nonvalvular atrial fibrillation were studied, using a nonimaging computerized nuclear probe linked to a personal computer. Left ventricular ejection fraction, end-diastolic and end-systolic volume counts, stroke volume counts and filling time were calculated on a beat-to-beat basis during 500 consecutive RR intervals. Multiple regression analysis was used to assess how ejection fraction was predicted by these variables.

RESULTS

The preceding RR interval and end-diastolic volume showed a positive relation, and prepreceding interval and end-systolic volume an inverse relation, with ejection fraction (all p < 0.001). Sensitivity analysis suggested that the preceding interval and the end-diastolic volume were equally important in predicting ejection fraction. There was a relatively strong interaction between the preceding interval and end-diastolic volume, indicating that the influence of the end-diastolic volume on ejection fraction was diminished after long intervals. A second interaction showed that the effect of end-diastolic volume on ejection fraction was attenuated after short prepreceding cycles.

CONCLUSIONS

Cycle length-dependent contractile mechanisms, including postextrasystolic potentiation and mechanical restitution, determine the varying left ventricular systolic performance during atrial fibrillation over the entire range of intervals. Beat-to-beat changes in preload, consistent with the Frank-Starling mechanism, also play a role, but their influence is diminished after long preceding and short prepreceding intervals.

Detecting abnormalities in left ventricular function during exercise by respiratory measurement

The degree of exercise-induced cardiac dysfunction and its relation to the anaerobic threshold were evaluated in 23 patients with chronic heart disease. A symptom-limited exercise test was performed with a cycle ergometer with work rate increased by 1 W every 6 seconds. Left ventricular function, as reflected by ejection fraction, was continuously monitored with a computerized cadmium telluride detector after the intravenous injection of technetium-labeled red blood cells. The anaerobic threshold (mean, 727 +/- 166 ml/min) was determined by the noninvasive measurement of respiratory gas exchange. As work rate rose, the left ventricular ejection fraction increased but reached a peak value at the anaerobic threshold and then fell below resting levels. Ejection fraction at rest, anaerobic threshold, and peak exercise were 41.4 +/- 11.3%, 46.5 +/- 12.0%, and 37.2 +/- 11.0%, respectively. Stroke volume also increased from rest (54.6 +/- 17.0 ml/beat) to the point of the anaerobic threshold (65.0 +/- 21.2 ml/beat) and then decreased at peak exercise (52.4 +/- 18.7 ml/beat). The slope of the plot of cardiac output versus work rate decreased above the anaerobic threshold. The anaerobic threshold occurred at the work rate above which left ventricular function decreased during exercise. Accurate determination of the anaerobic threshold provides an objective, noninvasive measure of the oxygen uptake above which exercise-induced deterioration in left ventricular function occurs in patients with chronic heart disease.

Nuclear ejection fraction measurements with a small crystal detector: methodological investigations

A series of studies were performed with a single crystal detector system, nuclear stethoscope (N.S.) (Bios) used for measuring left ventricular function (ejection fraction [EF]). Counting capacity, validity, reproducibility, effect of repositioning of the instrument and of different operators were investigated. Counting capacity was found to be approximately linear up to a count rate of 40.000 cps. Validity was studied by comparing measurements in the same subject using the N.S. with those obtained by a gamma-camera computer system with software using a background subtraction similar to that in the N.S. The mean difference in EF (0.01) was not significant. Maximum emptying and filling velocity measurements with the two instruments were also compared r = 0.86 and r = 0.89, respectively, and a coefficient of variation of 18.1% and 17.9%. Reproducibility was determined from duplicate determinations under identical conditions. The standard error of a single determination was 5%. Repositioning by the same operator increased the variation to 9.1% without any systematic difference. Comparison between two operators did not increase the coefficient of variation (8.8%). There was a systematic difference between measurements using the two acquisition modes, ventricular function mode and position monitor mode. Beat-to-beat variation of EF values during 12 s in 25 patients with coronary heart disease studied under standardized resting conditions was 11.9%.

Changes in left ventricular function during exercise and their relation to ST segment changes in patients with angina

The high count sensitivity of the non-imaging nuclear probe affords the possibility of measuring left ventricular ejection fraction continuously during short term interventions. The nuclear probe was used to examine the pattern of change of left ventricular function during dynamic exercise and its temporal relation to ST segment depression in 12 patients with stable exertional angina. After in vivo blood pool labelling with technetium-99m the left ventricular time-activity waveform was detected by the nuclear probe and was continuously recorded on a strip chart. The 15 beat mean ejection fraction and the ST segment level 80 ms after the J point were measured at rest and every 30 seconds during maximal ergometric exercise and during recovery. The mean ejection fraction was 54.3% (range 46-64%) at rest and fell during exercise in all subjects by a mean of 16.8% (range 6-25%). In contrast, in a control group of 16 healthy male volunteers the mean ejection fraction was 55.9% (range 47-64%) at rest and increased in all by a mean of 10.2% (range 3-19%) during exercise. The difference of ejection fraction response to exercise between the patients and controls was due to pronounced increases in relative end diastolic and especially end systolic volumes in the patients. Relative stroke volume differed between patients and controls only at peak exercise. ST segment depression greater than 1 mm developed in 11 of the 12 patients. A decrease of greater than 5% in ejection fraction occurred within 1 minute of starting exercise in nine of the 12, and in 11 patients it preceded the beginning of ST depression. In most of this selected group of patients the ejection fraction had fallen during exercise before the appearance of ischaemic electrocardiographic changes.

Measurement of left ventricular ejection fraction in pediatric patients using the nuclear stethoscope

Left ventricular (LV) ejection fraction (EF) was measured in 25 patients, aged 2 weeks to 20 years (mean 8.6 years), using a portable nonimaging scintillation stethoscope. Technically satisfactory studies were obtained in 23 patients. LVEF was validated by cineangiography in 19 patients and by standard gated blood pool scintigraphy in 4. EF measured by the nuclear stethoscope correlated well with values obtained by cineangiography or scintigraphy (r = 0.869, p less than 0.001) over a wide range of EF values (18 to 79%). In children younger than 5 years (n = 11), the correlation (r = 0.728, p less than 0.02) was less satisfactory than in those older than 5 years (r = 0.926; p less than 0.001). Although modifications in the instrument and further clinical trials with the stethoscope are needed before the device becomes clinically useful to pediatric cardiologists, our data indicate that the nuclear stethoscope can provide reliable assessment of LVEF in pediatric patients.

Continuous monitoring of left ventricular performance with the computerized nuclear probe during laryngoscopy and intubation before coronary artery bypass surgery

Left ventricular performance was monitored serially in 25 patients during laryngoscopy and intubation in the anesthetic induction period before elective coronary artery bypass surgery using the labeled equilibrium blood pool and the computerized nuclear probe. Left ventricular ejection fraction was obtained preoperatively, after induction of anesthesia but before endotracheal intubation, immediately after intubation, and at 1 minute intervals thereafter for 10 minutes. In all patients, there was an immediate decrease (mean 16%) in left ventricular ejection fraction accompanying the reflex hypertension and tachycardia occurring during laryngoscopy and endotracheal intubation; it was significantly depressed for 3 minutes with the concomitant hemodynamic changes. Seven patients did not demonstrate a recovery of left ventricular ejection fraction to the preintubation value. In 10 healthy noncardiac patients undergoing orthopedic surgery, after an identical anesthetic induction sequence and intubation, there was a similar decrease in ejection fraction, but of shorter duration. In these patients the recovery of left ventricular performance preceded the recovery of blood pressure and heart rate. This study demonstrates that profound decreases in left ventricular performance accompany the reflex hypertension and tachycardia occurring during endotracheal intubation and that there is persisting depression of left ventricular function in some patients with coronary artery disease. These findings indicate the potential utility of the computerized nuclear probe for monitoring ventricular performance during this critical period.