Anesth Analg 2009;109:114-118

Pulse wave analysis (PWA) allows cardiac output (CO) measurement after calibration by transpulmonary thermodilution. A PWA system that does not require previous calibration, the FloTrac/Vigileo (FTV), has been recently developed. We compared determinations of CO made with the FTV to simultaneous measurements using transesophageal echocardiography (TEE).

Methods
Ten ASA I-II patients scheduled for laparoscopic colorectal surgery were studied. A radial 20-gauge cannula was inserted and connected to a hemodynamic monitor and a FTV system for PWA and determination of CO (COPWA). TEE CO (COTEE) was determined as previously described. Measurements were made after intubation, 5 min after establishing the lithotomy position, 5 min after establishing pneumoperitoneum, every 30 min, or each time mean arterial blood pressure decreased below basal values. Statistical analysis was made with the Bland and Altman method.

Results
Eighty-eight measurements were compared. The COTEE values ranged from 3.23 to 12 Lt/min (mean 6.21 ± 1.85). Values for COPWA ranged from 2.9 to 8.5 Lt/min (mean 4.84 ± 1.14). Bias was 1.17 and limits of agreement −2.02 and 4.37. The percentage error between all COTEE and COPWA measurements was 40% (27%-50%) mean (range).

Conclusions
During laparoscopic colon surgery, clinically important differences were observed between CO determinations made with TEE and FTV.

JACC 2009;54:1012-1013

Aortic stenosis (AS) is the most frequent indication for valve replacement in Europe and North America, and correct diagnosis and timing of surgery are critical. Although it is evident that patients with symptoms attributable to severe AS require prompt valve replacement, there remain some unresolved issues in clinical decision making.

This study was designed to examine the prognostic value of valvuloarterial impedance (Zva) in patients with aortic stenosis (AS).

We previously showed that the Zva is superior to standard indexes of AS severity in estimating the global hemodynamic load faced by the left ventricle (LV) and predicting the occurrence of LV dysfunction. This index is calculated by dividing the estimated LV systolic pressure (systolic arterial pressure + mean transvalvular gradient) by the stroke volume indexed for the body surface area.

Methods
We retrospectively analyzed the clinical and echocardiographic data of 544 consecutive patients having at least moderate AS (aortic jet velocity =2.5 m∑s-1) and no symptoms at baseline. The primary end point for this study was the overall mortality regardless of the realization of aortic valve replacement (AVR).

Results
Four-year survival was significantly (p < 0.001) lower in the patients with a baseline Zva =4.5 mm Hg∑ml-1∑m2 (65 ± 5%) compared with those with Zva between 3.5 and 4.5 mm Hg∑ml-1∑m2 (78 ± 4%) and those with Zva =3.5 mm Hg∑ml-1∑m2 (88 ± 3%). The risk of mortality was increased by 2.76-fold in patients with Zva =4.5 mm Hg∑ml-1∑m2 and by 2.30-fold in those with a Zva between 3.5 and 4.5 mm Hg∑ml-1∑m2 after adjusting for other risk factors and type of treatment (surgical vs. medical).

Conclusions
Increased Zva is a marker of excessive LV hemodynamic load, and a value >3.5 successfully identifies patients with a poor outcome. These findings suggest that beyond standard indexes of stenosis severity, the consideration of Zva may be useful to improve risk stratification and clinical decision making in patients with AS.

Crit Care Med 2009; 37:1696-1701

Weaning-induced pulmonary edema is a cause of weaning failure in high-risk patients. The diagnosis may require pulmonary artery catheterization to demonstrate increased pulmonary artery occlusion pressure (PAOP) during weaning. Transthoracic echocardiography can estimate left ventricular filling pressures using early (E) and late (A) peak diastolic velocities measured with Doppler transmitral flow, and tissue Doppler imaging of mitral annulus velocities including early (Ea) peak diastolic velocity. We tested the hypothesis that E/A and E/Ea could be used to detect weaning-induced PAOP elevation defined by a PAOP >=18 mm Hg during a spontaneous breathing trial (SBT).

Measurements and main results
We included 39 patients who previously failed two consecutive SBTs. A third SBT was performed over a maximum 1-hour period using a T-piece. The PAOP, E/A, and E/Ea were measured before and during this SBT. Receiver operating characteristic curves were constructed to determine the optimal sensitivity and specificity values of E/A and E/Ea obtained at the end of the SBT for predicting a weaning-induced PAOP elevation. Weaning-induced PAOP elevation occurred in 17 patients. A value of E/A >0.95 at the end of the SBT predicted weaning-induced PAOP elevation with a sensitivity of 88% and a specificity of 68%. A value of E/Ea >8.5 at the end of the SBT predicted weaning-induced PAOP elevation with a sensitivity of 94% and a specificity of 73%. The combination of E/A >0.95 and E/Ea >8.5 predicted a weaning-induced PAOP elevation with a sensitivity of 82% and a specificity of 91%.

Conclusion
At the end of an SBT, the combination of E/A >0.95 and E/Ea >8.5 measured with transthoracic echocardiography allowed an accurate noninvasive detection of weaning-induced PAOP elevation.

JAMA. 2009;301:286-294

Limited information exists regarding the role of left ventricular function in predicting exercise capacity and impact on age- and sex-related differences.

Objectives
To determine the impact of measures of cardiac function assessed by echocardiography on exercise capacity and to determine if these associations are modified by sex or advancing age.

Design
Cross-sectional study of patients undergoing exercise echocardiography with routine measurements of left ventricular systolic and diastolic function by 2-dimensional and Doppler techniques. Analyses were conducted to determine the strongest correlates of exercise capacity and the age and sex interactions of these variables with exercise capacity.

Setting
Large tertiary referral center in Rochester, Minnesota, in 2006.

Participants
Patients undergoing exercise echocardiography using the Bruce protocol (N = 2867). Patients with echocardiographic evidence of exercise-induced ischemia, ejection fractions lower than 50%, or significant valvular heart disease were excluded.

Main outcome measure
Exercise capacity in metabolic equivalents (METs).

Results
Diastolic dysfunction was strongly and inversely associated with exercise capacity. Compared with normal function, after multivariate adjustment, those with moderate/severe resting diastolic dysfunction (–1.30 METs; 95% confidence interval [CI], –1.52 to –0.99; P < .001) and mild resting diastolic dysfunction (–0.70 METs; 95% CI, –0.88 to –0.46; P < .001) had substantially lower exercise capacity. Variation of left ventricular systolic function within the normal range was not associated with exercise capacity. Left ventricular filling pressures measured by resting E/e’ of 15 or greater (–0.41 METs; 95% CI, –0.70 to –0.11; P = .007) or postexercise E/e’ of 15 or greater (–0.41 METs; 95% CI, –0.71 to –0.11; P = .007) were similarly associated with a reduction in exercise capacity, each in separate multivariate analyses. Individuals with impaired relaxation (mild dysfunction) or resting E/e’ of 15 or greater had a progressive increase in the magnitude of reduction in exercise capacity with advancing age (P < .001 and P = .02, respectively). Other independent correlates of exercise capacity were age (unstandardized β coefficient, –0.85 METs; 95% CI, –0.92 to –0.77, per 10-year increment; P < .001), female sex (–1.98 METs; 95% CI, –2.15 to –1.84; P < .001), and body mass index greater than 30 (–1.24 METs; 95% CI, –1.41 to –1.10; P < .001).

Conclusion
In this large cross-sectional study of those referred for exercise echocardiography and not limited by ischemia, abnormalities of left ventricular diastolic function were independently associated with exercise capacity.

Crit Care Med 2008;36:1701-1706

To evaluate the actual incidence of global left ventricular hypokinesia in septic shock.

Method
All mechanically ventilated patients treated for an episode of septic shock in our unit were studied by transesophageal echocardiography, at least once a day, during the first 3 days of hemodynamic support. In patients who recovered, echocardiography was repeated after weaning from vasoactive agents. Main measurements were obtained from the software of the apparatus. Global left ventricular hypokinesia was defined as a left ventricular ejection fraction of <45%.

Measurements and Main Results
During a 3-yr period (January 2004 through December 2006), 67 patients free from previous cardiac disease, and who survived for >48 hrs, were repeatedly studied. Global left ventricular hypokinesia was observed in 26 of these 67 patients at admission (primary hypokinesia) and in 14 after 24 or 48 hrs of hemodynamic support by norepinephrine (secondary hypokinesia), leading to an overall hypokinesia rate of 60%. Left ventricular hypokinesia was partially corrected by dobutamine, added to a reduced dosage of norepinephrine, or by epinephrine. This reversible acute left ventricular dysfunction was not associated with a worse prognosis.

Conclusion
Global left ventricular hypokinesia is very frequent in adult septic shock and could be unmasked, in some patients, by norepinephrine treatment. Left ventricular hypokinesia is usually corrected by addition of an inotropic agent to the hemodynamic support.

Anaesthesia 2008;63:482-487

Heart failure is a major risk factor for adverse postoperative events following non-cardiac surgery. The use of transthoracic echocardiogram as a pre-operative investigation to assess cardiac dysfunction has limitations in this setting. The N-Terminal fragment of B-Type natriuretic peptide (NT proBNP) has been used in screening for heart failure. We have investigated the use of NT proBNP as a screening tool for left ventricular systolic dysfunction to reduce the requirement for pre-operative echocardiograms. Ninety-eight pre-operative non-cardiac surgical patients scheduled to undergo echocardiography were assessed clinically and with an NT proBNP measurement. Echocardiogram was used to define two groups of patients depending on the presence or absence of abnormal left ventricular function and the NT proBNP level was compared between the groups using non-parametric and receiver-operator-characteristic (ROC) curve analysis. In terms of pre-operative screening, a NT proBNP of <38.2 pmol.l⁻¹ had a 100% negative predictive value in predicting patients with normal left ventricular systolic function and would have prevented the requirement for echocardiogram in 43% of pre-operative patients. NT proBNP was superior to electrocardiological and clinical criteria for detection of a normal echocardiogram. This may have significant impact in the pre-operative assessment of patients undergoing non-cardiac surgery.

J Am Coll Cardiol 2008; 51:1127-1147

The American College of Cardiology Foundation (ACCF) and the American Society of Echocardiography (ASE) together with key specialty and subspecialty societies, conducted an appropriateness review for stress echocardiography. The review assessed the risks and benefits of stress echocardiography for several indications or clinical scenarios and scored them on a scale of 1 to 9 (based upon methodology developed by the ACCF to assess imaging appropriateness). The upper range (7 to 9) implies that the test is generally acceptable and is a reasonable approach, and the lower range (1 to 3) implies that the test is generally not acceptable and is not a reasonable approach. The midrange (4 to 6) indicates a clinical scenario for which the indication for a stress echocardiogram is uncertain.

The indications for this review were drawn from common applications or anticipated uses, as well as from current clinical practice guidelines. Use of stress echocardiography for risk assessment in patients with coronary artery disease (CAD) was viewed favorably, while routine repeat testing and general screening in certain clinical scenarios were viewed less favorably. It is anticipated that these results will have a significant impact on physician decision making and performance, reimbursement policy, and will help guide future research.

Am Fem Physician 2007;73:841-846

Diastolic heart failure occurs when signs and symptoms of heart failure are present but left ventricular systolic function is preserved (i.e., ejection fraction greater than 45 percent). The incidence of diastolic heart failure increases with age; therefore, 50 percent of older patients with heart failure may have isolated diastolic dysfunction. With early diagnosis and proper management the prognosis of diastolic dysfunction is more favorable than that of systolic dysfunction. Distinguishing diastolic from systolic heart failure is essential because the optimal therapy for one may aggravate the other. Although diastolic heart failure is clinically and radiographically indistinguishable from systolic heart failure, normal ejection fraction and abnormal diastolic function in the presence of symptoms and signs of heart failure confirm diastolic heart failure. The pharmacologic therapies of choice for diastolic heart failure are angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, diuretics, and beta blockers.

Cardiovascular morbidity and mortality resulting from congestive heart failure are major concerns for the critical care physician. Although heart failure is commonly associated with impaired systolic function, in up to one half of cases, heart failure occurs exclusively on the basis of an impairment of diastolic function. Diastole is the summation of processes by which the heart loses its ability to generate force and shorten and returns to its precontractile state. The two principal processes responsible for diastole are relaxation and passive pressure-volume properties of the ventricle. Echocardiography provides a comprehensive, noninvasive evaluation of diastolic filling of the ventricle, myocardial relaxation, and ventricular stiffness; the information obtained by echocardiography has prognostic value and is a guide to proper therapy. This article reviews the physiology of diastole, the pathogenesis of diastolic heart failure, and the diagnosis of diastolic dysfunction, with a focus on the diagnostic utility of echocardiography and an emphasis on those areas of greatest interest to the critical care physician.

Critical Care 2007, 11:R43

Conventional pulsed wave Doppler parameters are known to be preload dependent, whereas newly proposed Doppler indices may be less influenced by variations in loading conditions. The aim of the present study was to evaluate the effects of haemodialysis-induced preload reduction on both conventional and new Doppler parameters for the assessment of left ventricular (LV) diastolic function.

Methods
This prospective observational study was conducted in a medical-surgical intensive care unit (ICU) and nephrology department of a teaching hospital. In total, 37 haemodialysis patients with end-stage renal disease (age [mean ± standard deviation]: 52 ± 13 years) and eight ventilated ICU patients with acute renal failure receiving vasopressor therapy (age 57 ± 16 years; Simplified Acute Physiology Score II 51 ± 17) were studied. Echocardiography was performed before and after haemodialysis. Conventional pulsed wave Doppler indices of LV diastolic function as well as new Doppler indices, including Doppler tissue imaging early diastolic velocities (E’ wave) of the septal and lateral portions of the mitral annulus, and propagation velocity of LV inflow at early diastole (Vp) were measured and compared before and after ultrafiltration.

Results
The volume of ultrafiltration was greater in haemodialysis patients than in ICU patients (3.0 ± 1.1 l versus 1.9 ± 0.9 l; P = 0.005). All conventional pulsed wave Doppler parameters were altered by haemodialysis. In haemodialysis patients, E’ velocity decreased after ultrafiltration when measured at the septal mitral annulus (7.1 ± 2.5 cm/s versus 5.9 ± 1.7 cm/s; P = 0.0003), but not at its lateral portion (8.9 ± 3.1 cm/s versus 8.3 ± 2.6 cm/s; P = 0.37), whereas no significant variation was observed in ICU patients. Vp decreased uniformly after ultrafiltration, the difference being significant only in haemodialysis patients (45 ± 11 cm/s versus 41 ± 13 cm/s; P = 0.04). Although of less magnitude, ultrafiltration-induced variations in Doppler parameters were also observed in haemodialysis patients with altered LV systolic function.

Conclusion
In contrast to other Doppler parameters, Doppler tissue imaging E’ maximal velocity measured at the lateral mitral annulus represents an index of LV diastolic function that is relatively insensitive to abrupt and marked preload reduction.

J Am Coll Cardiol, 2007; 50:187-204

The American College of Cardiology Foundation (ACCF) and the American Society of Echocardiography (ASE), together with key specialty and subspecialty societies, conducted an appropriateness review for transthoracic and transesophageal echocardiography (TTE/TEE). This review assesses the risks and benefits of TTE and/or TEE for several indications or clinical scenarios and scored them based on a scale of 1 to 9. The upper range (7 to 9) implies that the test is generally acceptable and is a reasonable approach, and the lower range (1 to 3) implies that the test is generally not acceptable and is not a reasonable approach. The midrange (4 to 6) indicates a clinical scenario for which the indication for an echocardiogram is uncertain.

The indications for this review were drawn from common applications or anticipated uses as well as current clinical practice guidelines. Use of TTE/TEE for initial evaluation of structure and function was viewed favorably, while routine repeat testing and general screening uses in certain clinical scenarios were viewed less favorably. It is anticipated that these results will have a significant impact on physician decision-making and performance, reimbursement policy, and will help guide future research.