Echocardiography in the critically ill: current and potential roles.

BACKGROUND: The use of echocardiography in the critically ill presents specific challenges. However, information of direct relevance to clinical management can be obtained relating to abnormalities of structure and function and can be used to estimate pulmonary arterial and venous pressures. DISCUSSION: Investigation of the consequences of myocardial ischaemia, valvular dysfunction and pericardial disease can be facilitated, and changes characteristic of specific conditions (e.g. sepsis, pulmonary thromboembolism) detected. Echocardiography can also be used to monitor the effects of therapeutic interventions. CONCLUSIONS: The applications of echocardiography in the critical care setting (excluding standard peri-operative echocardiography for cardiac surgery) are reviewed, with particular emphasis on the assessment of cardiac physiology.

Management of tuberculous constrictive pericarditis and tuberculous pericardial effusion in Transkei: results at 10 years follow-up.

BACKGROUND: Tuberculous pericarditis is common in Transkei (Eastern Cape). Two randomized trials showed benefits at two years for prednisolone in patients with constrictive pericarditis, and open drainage plus prednisolone in patients with pericardial effusion. AIM: To see whether the advantages of prednisolone and open drainage were maintained up to 10 years. DESIGN: Follow-up of randomized, double-blind, placebo-controlled trials. METHODS: All 383 patients (143 constriction, 240 effusion) received the same anti-tuberculosis chemotherapy. They were randomized to prednisolone or placebo for the first 11 weeks, and were followed-up over 10 years. Among the 240 with effusion, 122 were also randomized to immediate open surgical drainage of pericardial fluid versus pericardiocentesis as required. Adverse outcomes were: death from pericarditis, pericardiectomy, repeat pericardiocentesis, and subsequent open drainage. RESULTS: The 10-year follow-up rate was 96%. In constriction patients, adverse outcomes occurred in 19/70 (27%) prednisolone vs. 28/73 (38%) placebo (p = 0.15), deaths from pericarditis being 2 (3%) vs. 8 (11%), respectively (p = 0.098, Fisher's exact test). In effusion patients, adverse outcomes occurred in 14/27 (52%) with neither drainage nor prednisolone, vs. 4/29 (14%) drainage and prednisolone, 4/35 (11%) drainage and placebo, and 6/31 (19%) prednisolone and no drainage (p = 0.08 for interaction). Drainage eliminated the need for repeat pericardiocentesis. In the 176 with effusion and no drainage, adverse outcomes occurred in 17/88 (19%) prednisolone vs. 35/88 (40%) placebo patients (p = 0.003), with repeat pericardiocentesis 20 (23%) placebo vs. 9 (10%) prednisolone (p = 0.025). In a multivariate survival analysis (stratified by type of pericarditis), prednisolone reduced the overall death rate after adjusting for age and sex (p = 0.044), and substantially reduced the risk of death from pericarditis (p = 0.004). At 10 years, the great majority of surviving patients in all treatment groups were either fully active or out and about, even if activity was restricted. DISCUSSION: In the absence of a clear contraindication, a corticosteroid should be used in addition to antituberculosis chemotherapy in the management of patients with tuberculous pericarditis.

Incremental changes in QRS duration in serial ECGs over time identify high risk elderly patients with heart failure.

AIMS: To investigate the hypothesis that changes in the ECG over time may be an important and readily available marker of prognostic value in patients with heart failure. METHODS: 112 elderly patients (81 men) with stable heart failure, a mean (SD) age of 73.3 (4.4) years, left ventricular ejection fraction 38 (17)%, and peak oxygen consumption 15.1 (4.7) ml/kg/min had ECG measurements on two occasions a minimum of 12 (5) months apart. RESULTS: During the subsequent follow up period (mean 27 (17) months) 45 patients died. QRS duration (p = 0.001) and heart rate (p = 0.03) at baseline were found by Cox proportional hazard method analysis to predict adverse outcomes in these patients. Of the changes in ECG parameters between the first and second visit, broadening of QRS duration (p = 0.001) predicted mortality. On Kaplan-Meier survival analysis, patients with < 5% change in QRS duration had fewer end points than patients with 5-20% change. A > 20% increase in QRS duration was associated with the worst prognosis. Progressive prolongation of QRS duration correlated closely with deterioration of LV systolic and diastolic function. CONCLUSION: A single measurement of QRS duration has significant prognostic value in elderly patients with heart failure and the increase in QRS duration over time is an even better predictor of adverse out comes.

Disturbed atrioventricular electromechanical function long after Mustard operation for transposition of great arteries: a potential contributing factor to atrial flutter.

OBJECTIVE: The objectives were to study atrial and ventricular electromechanical function in patients long after Mustard repair for transposition of great arteries and to identify possible causes and physiologic disturbances in those with recurrent atrial flutter. METHODS: Electromechanical atrial and ventricular function was assessed in 22 patients (11 women) aged 27 +/- 5 years, 10 to 29 (mean 24) years after initial Mustard operation with electrocardiography and echocardiography. The study subjects involved 12 patients with documented atrial flutter and the remaining 10 without history of atrial arrhythmia served as controls. All patients were studied while in sinus rhythm. RESULTS: There was no difference in age, gender, or age at original Mustard surgery between the 2 patient groups. The P wave and QRS duration were significantly broader in patients compared with controls (128 +/- 14 ms vs 100 +/- 10 ms, P <.05 and 120 +/- 20 ms vs 93 +/- 6 ms, P <.01). Right ventricular end diastolic dimension was not different, whereas left ventricular fraction shortening was less (20% +/- 10% vs 35% +/- 12%, P <.01) in the patient group. Left and septal total ventricular long axes amplitude were significantly lower in patients compared with controls (1.4 +/- 0.4 cm vs 1.7 +/- 0.3 cm, P <.05 and 0.6 +/- 0.2 cm vs 1.0 +/- 0.3 cm, P <.01). Right-sided total long axis excursion was equally reduced in the 2 groups (1.0 +/- 0.3 cm). Septal and right-sided but not left-sided "a" wave was smaller in the patients (1.2 +/- 1 mm vs 3 +/- 1.2 mm, P <.001 and 1 +/- 1.3 mm vs 3 +/- 0.9 mm, P <.01). Right atrial electromechanical delay was significantly longer in patients with respect to controls (110 +/- 14 ms vs 84 +/- 25 ms, P <.001), but on the left there was no difference. The P wave duration correlated closely with right atrial electromechanical delay, r = 0.79, P <.003. Significant tricuspid regurgitation was found in 9 of 12 patients but none of the controls. CONCLUSION: Right ventricular dysfunction is present long after Mustard operation for transposition of great arteries whether flutter occurs. However, in patients with history of atrial flutter, evidence of left ventricular dysfunction, significant tricuspid regurgitation, impaired right atrial electrical and mechanical function, and reversed onset of atrial systole is also present. The consistent association of the disturbed atrial and ventricular electromechanical behavior suggests a multifactorial etiology for atrial arrhythmia.

Arterial waves in humans during peripheral vascular surgery.

The purpose of this study was to investigate the effect of aortic clamping on arterial waves during peripheral vascular surgery. We measured pressure and velocity simultaneously in the ascending aorta, in ten patients (70+/-5 years) with aortic-iliac disease intra-operatively. Pressure was measured using a catheter tip manometer, and velocity was measured using Doppler ultrasound. Data were collected before aortic clamping, during aortic clamping and after unclamping. Hydraulic work in the aortic root was calculated from the measured data, the reflected waves were determined by wave-intensity analysis and wave speed was determined by the PU-loop (pressure-velocity-loop) method; a new technique based on the 'water-hammer' equation. The wave speed is approx. 32% (P<0.05) higher during clamping than before clamping. Although the peak intensity of the reflected wave does not alter with clamping, it arrives 30 ms (P<0.05) earlier and its duration is 25% (P<0.05) longer than before clamping. During clamping, left ventricule (LV) hydraulic systolic work and the energy carried by the reflected wave increased by 27% (P<0.05) and 20% (P<0.05) respectively, compared with before clamping. The higher wave speed during clamping explains the earlier arrival of the reflected waves suggesting an increase in the afterload, since the LV has to overcome earlier reflected compression waves. The longer duration of the reflected wave during clamping is associated with an increase in the total energy carried by the wave, which causes an increase in hydraulic work. Increased hydraulic work during clamping may increase LV oxygen consumption, provoke myocardial ischaemia and hence contribute to the intra-operative impairment of LV function known in patients with peripheral vascular disease.

Assessment of cardiac risk before peripheral vascular surgery: a comparison of myocardial perfusion imaging and long axis echocardiography at rest.

OBJECTIVE: To compare resting long axis echocardiography with adenosine thallium-201 emission tomography in detecting myocardial ischaemic abnormalities and surgical related risk in patients before peripheral vascular surgery. DESIGN: A prospective and blinded pre-operative examination of resting left ventricular minor and long axes and myocardial perfusion during adenosine vasodilation using thallium-201 emission tomography. SETTING: A tertiary referral centre for cardiac and vascular disease equipped with invasive, non-invasive and surgical facilities. SUBJECTS: 65 patients (40 male) with significant peripheral vascular disease, mean age 63+/-10 (S.D.) years, and 21 normal subjects of similar age. RESULTS: Thallium-201 myocardial perfusion tomography was abnormal in 50/65 patients; 27 had fixed, 23 reversible abnormalities (19 of whom had both). Long axis was considered abnormal if one or more of two systolic long axis disturbances, reduced extent of total excursion <1 cm at any of the three (left, septal and posterior left ventricular) sites or prolonged shortening >1 mm after A2, and two diastolic abnormalities, delayed onset of lengthening >80 ms after A2 or reduced peak lengthening velocity <4.5 cm/s, was present. Long axis score (maximum 12) was based on the presence or absence of these four disturbances at each of the three sites. Myocardial perfusion imaging with thallium-201 classified the patients into three different groups according to their liability to low, moderate or high surgical risk (summed stress perfusion score of 36). Thirteen of 50 patients were identified as subjects at high surgical risk, with a perfusion score of 22/36 and below. Twelve of these demonstrated significantly greater impairment of systolic and diastolic long axis function, compared to those at low surgical risk, with a total long axis echo score of 6/12 or more. Seventeen of 18 patients identified as being at low surgical risk, with a perfusion score of 32/36 and above, had total long axis score of less than 6/12. The remaining 19 moderate risk patients had a wide range of long axis scores. In the 65 patients studied there were two post-operative deaths, one post-discharge death due to cerebrovascular accident, and one due to renal failure. CONCLUSION: The combination of both systolic and diastolic long axis disturbances in patients with peripheral vascular disease can be used to predict the thallium assessment of surgical risk. Long axis echocardiography may thus have value as a screening test before non-cardiac surgery as well as providing a means of monitoring myocardial perfusion.

Long axis electromechanics during dobutamine stress in patients with coronary artery disease and left ventricular dysfunction.

OBJECTIVE: To dissociate the effect of inotropy from activation change during dobutamine stress on left ventricular long axis function in patients with coronary artery disease (CAD). METHODS: 25 patients with CAD and normal left ventricular cavity size and 30 with cavity dilatation-18 with normal activation (DCM-NA) and 12 with left bundle branch block (DCM-LBBB)-were compared with 20 controls. 12 lead ECG and septal long axis echograms were assessed at rest and peak dobutamine stress. Amplitude, shortening and lengthening velocities, postejection shortening, Q wave to onset of shortening (Q-OS), and A2 to onset of lengthening (A2-OL) were measured. Inotropy was evaluated from peak aortic acceleration. RESULTS: In controls, amplitude, shortening and lengthening velocities, and peak aortic acceleration increased with stress; QRS, Q-OS, and A2-OL shortened (all p < 0.001); and contraction remained coordinate. In the group of patients with CAD and normal left ventricular cavity size, shortening velocity and peak aortic acceleration increased with stress (p < 0.005). However, amplitude and lengthening velocity did not change, QRS, Q-OS, and A2-OL lengthened (p < 0.01), and incoordination appeared. Results were similar in the group with DCM-NA. In the DCM-LBBB group, shortening velocity and peak aortic acceleration increased modestly with stress (p < 0.01) but amplitude, lengthening velocity, QRS, Q-OS, A2-OL, and incoordination remained unchanged. Overall, change in shortening velocity correlated with that in peak aortic acceleration (r(2) = 0.71), in amplitude with that in lengthening velocity (r(2) = 0.74), and in QRS with both Q-OS (r(2) = 0.69) and A2-OL (r(2) = 0.63). CONCLUSION: The normal long axis response to dobutamine reflects both inotropy and rapid activation. In CAD, inotropy is preserved with development of ischaemia but the normal increase in amplitude is lost and prolonged activation delays the time course of shortening, causing pronounced incoordination. Overall, shortening rate uniformly reflects inotropy while lengthening rate depends mainly on systolic amplitude rather than primary diastolic involvement, even with overt ischaemia.

Mitral annulus dynamics: determinants of left ventricular filling.

OBJECTIVES: To examine the influence of mitral annular dynamics on left ventricular filling. METHODS: Twenty patients (mean age 64 +/- 6 years) with coronary artery disease and normal left ventricular function were studied by transesophageal echocardiography immediately before bypass grafting with the pericardium open. Pulmonary venous and transmitral velocities were recorded with pulsed wave Doppler. Mitral annulus position was derived by M-mode and its rate of change by digitisation of the records. From simultaneous high fidelity left atrial pressure, instantaneous power and its time integral work were derived. RESULTS: In all patients the power curve was triphasic, being positive in both early and late diastole and negative during ventricular systole. Systolic annular work was related to pulmonary venous peak systolic velocities (r = 0.74, p < 0.001). The ratio of the early to late diastolic annular work correlated with the transmitral E/A ratio (r = 0.82, p < 0.0001) and early diastolic work was related to pulmonary venous peak diastolic velocities (r = 0.74, p < 0.001). Pressure-displacement curves of the annulus throughout the period of rapid ventricular filling were curvilinear with instantaneous stiffness increasing with distension. In addition all curves demonstrated a diastolic equilibrium point of zero stiffness. CONCLUSIONS: Mitral annulus function, particularly when work and power are calculated, appear to be an important determinant of left ventricular filling. The underlying mechanics may also explain the variations in transmitral and pulmonary venous Doppler patterns seen in diseased states.

Electromechanical interrelations during dobutamine stress in normal subjects and patients with coronary artery disease: comparison of changes in activation and inotropic state.

OBJECTIVE: To identify the effects of altered ventricular activation during dobutamine stress on left ventricular function in normal subjects and in patients with coronary artery disease, and to distinguish these from an inotropic response. DESIGN: Prospective analysis of 12 lead ECG and echocardiogram at rest and at peak stress. SETTING: Tertiary referral centre for cardiac disease equipped with non-invasive facilities for pharmacological stress testing. METHODS: 22 patients with coronary artery disease were compared with 17 age matched controls. Left ventricular ejection and filling patterns were assessed using Doppler echocardiography. Activation effects were correlated with relative left ventricular ejection and filling times, and the Z ratio ([left ventricular ejection + filling times]/RR interval). Inotropic response was measured from peak aortic acceleration. RESULTS: In controls, QRS shortened (by 4 ms, p < 0.001), and total ejection and filling periods lengthened (by 2 s/min, p < 0.01 and 5 s/min, p < 0.001, respectively). The Z ratio thus increased and correlated with QRS shortening (r(2) = 0.69). Peak aortic acceleration (PAA) increased by 135%, p < 0.001. In patients, QRS lengthened at peak stress (by 9 ms, p < 0.001). Total ejection and filling times did not change, but Z ratio fell, correlating with QRS prolongation (r(2) = 0.65). Nevertheless, PAA increased by 63%, p < 0.001. CONCLUSIONS: Relative ejection and filling times reflect ventricular activation at rest and during stress independent of changes in inotropic state. By contrast, peak aortic acceleration reflects the positive inotropic effect of dobutamine on the myocardium, regardless of changes in activation.

Right ventricular dysfunction in adult severe cystic fibrosis.

STUDY OBJECTIVES: This study sought to assess the extent of impairment of cardiac function in adult patients with end-stage cystic fibrosis (CF) and to examine the relationship between cardiovascular abnormalities and the degree of hypoxemia and hypercapnia. DESIGN AND SETTING: A retrospective study in a tertiary cardiac and CF center. PARTICIPANTS AND INTERVENTIONS: A total of 103 adult patients with end-stage CF awaiting lung or heart and lung transplantation (mean age [+/- SD], 26+/-7 years; 54 men) underwent Doppler echocardiography and arterial blood gas analysis (mean PaO(2), 54+/-10 mm Hg; mean PaCO(2), 47+/-8 mm Hg). The findings were compared to those of 17 healthy control subjects (mean age, 24+/-7 years; 13 men) who had no history of cardiac or pulmonary disease. MEASUREMENTS AND RESULTS: All patients were in sinus rhythm with a mean tachycardia of 112+/-18 beats/min (control subjects, 76+/-16; p<0.0001) and had a cardiac output of 5.3 L/min (control subjects, 4.3 L/min; p<0.04). In the patient group, the left ventricular (LV) dimensions, systolic and diastolic function, and wall thickness were all within normal limits. The mean amplitude of long-axis excursion in patients was normal at the LV site, but that of the right ventricular (RV) free wall was significantly reduced as compared with control subjects (1.6+/-0.4 vs. 2.2+/-0.4 cm, respectively; p<0.001), which was found to correlate with the degree of hypoxemia (r = 0.63; p<0.02) and hypercapnia (r = -0.68; p<0.01). RV diastolic function, which was represented by the relative isovolumic relaxation time to cardiac cycle length, was longer in patients than in control subjects (8.7+/-4.8% vs. 5.0+/-3.0%, respectively; p<0.03). The pulmonary flow acceleration time (90+/-22 vs 121+/-34 ms, respectively; p<0.01) and the systolic stroke distance (7.0+/-2.2 vs. 10.5+/-1.9 cm/s(2); p<0.001) were both lower than normal. CONCLUSIONS: This study confirms the presence of significant RV systolic and diastolic dysfunction in the setting of consistent tachycardia and increased cardiac output in adult CF patients with severe disease. No specific LV abnormalities were detected in these patients.

Different response of patients with idiopathic and ischaemic dilated cardiomyopathy to exercise training.

We looked at the benefits and complications of a home-based exercise programme in patients with ischaemic and idiopathic dilated cardiomyopathy. Twenty-four patients with left ventricular end-diastolic dimension >6.5 cm and fractional shortening <25% entered a cross-over trial of 8 weeks training versus 8 weeks rest. Echocardiography, electrocardiogram and cardiopulmonary exercise testing were performed at baseline, after training and after detraining. Training resulted in a higher peak oxygen consumption (26.5 versus 21.3 ml/kg/min, P=0.004), a higher peak heart rate (161 versus 152 bpm, P=0.02) and improved well-being. Patients with idiopathic dilated cardiomyopathy showed a significant increase in exercise time (879 versus 828 s, P=0.03) and peak oxygen consumption (31.3 versus 24.3 ml/kg/min, P=0.02) and a decrease in left ventricular end-diastolic dimension (6.4 versus 6.9 cm, P=0.01) and end-systolic dimension (5.3 versus 5.8 cm, P=0.04) in contrast to those with coronary artery disease, who developed a reduction in septal excursion and shortening rate following training. Complications of training were more common in those patients with ischaemic cardiomyopathy, greater left ventricular dimensions, poorer exercise tolerance and greater ventilation drive at baseline, and included fluid retention and exercise-induced ventricular tachycardia. We found that this group of patients with a dilated, poorly functioning left ventricle can safely derive benefit from a home-based exercise programme, particularly those of idiopathic origin, but they should be closely monitored for the development of complications.

Echocardiographic determinants of mortality in patients >67 years of age with chronic heart failure.

This study sought to assess the prognostic significance of echocardiographic measurements of left and right ventricular dimensions and function in patients >67 years of age with chronic congestive heart failure (CHF). This is a retrospective follow-up of elderly patients who underwent an echocardiography in the tertiary cardiac center. A total of 185 patients (131 men) aged >/=68 years (mean +/- SD 75 +/- 5) with CHF were enrolled into the study. After undergoing a detailed echocardiographic examination, all patients were followed-up for a median of 20 months (interquartile range 9 to 36). During the follow-up period 54 patients (29%) died. Left ventricular (LV) M-mode isovolumic relaxation time (IVRT), end-diastolic and end-systolic diameters, fractional shortening and mass, transmitral E:A ratio, and left atrial dimension, as well as New York Heart Association class and the age were found by Cox proportional-hazards univariate analyses to predict the outcome in these patients (all p <0.05). In multivariate analyses including these measurements, LV IVRT (p <0.04), age (p <0.03), and New York Heart Association class (p <0.001) were found to be the independent predictors of outcome. In the Kaplan-Meier analysis, patients with LV IVRT >30 ms had a better prognosis at 3 years (cumulative survival 78% [95% confidence interval 65% to 91%]) than those with LV IVRT 67 years of age with CHF. LV M-mode IVRT is among the most important independent predictors of outcome in this population.

True shape and area of proximal isovelocity surface area (PISA) when flow convergence is hemispherical in valvular regurgitation.

The proximal isovelocity surface area (PISA) method for quantifying valvular regurgitation uses an echocardiographic image with superimposed colour Doppler mapping to visualise the contours of velocity in the blood travelling towards the regurgitant orifice. The flux of blood through the regurgitant orifice is obtained as the product of the area of one of these (presumed hemispherical) contours and the speed of the blood passing through it. However, colour Doppler mapping measures the velocity component towards the echo probe (v cos theta;) rather than speed (v), so that the contours of equal Doppler velocity (isodoppler velocity contours) differ from isospeed contours. We derive the shape of the isodoppler contour surface obtainable by colour Doppler mapping, and show that its area is much less than that of the hemispherical isospeed contour. When regurgitant flux is derived from an appropriate single measure of contour dimension, an appropriate result may be obtained. However, if the true echocardiographic surface area is measured directly, the regurgitant flux will be substantially underestimated. Indeed, the conditions necessary for isodoppler velocity contours to be hemispherical are extraordinary. We should not therefore make deductions from the apparent shape for the convergence zone without considering the principles by which the image is generated. The discrepancy will assume practical significance when increased resolution of colour Doppler technology makes measurement of apparent surface area feasible. Assuming the flow contours are indeed hemispherical, a 'correction' factor of 1.45 would be required.

Relation of changes over time in ventricular size and function to those in exercise capacity in patients with chronic heart failure.

BACKGROUND: We studied the direction and magnitude of changes in left ventricular (LV) cavity size and mass over time and whether these changes were related to those in exercise performance in patients with chronic heart failure (CHF). METHODS AND RESULTS: The study group was composed of 59 patients (55 men aged 58 +/- 10 years) with CHF and LV end-diastolic diameter (EDD) >55 mm. All underwent echocardiography and a treadmill cardiopulmonary exercise test within a 4-week interval (baseline) and again after a period of >/=4 months (median of 14 months). At baseline, the group as a whole had moderate to severe LV dysfunction with an EDD of 70 +/- 9 mm, end-systolic diameter (ESD) of 60 +/- 11 mm, and LV mass of 500 +/- 200 g. The mean peak oxygen consumption (Vo (2), 18 +/- 6 mL/kg per minute) was unrelated to LV cavity size or mass. EDD increased in 37 (63%) of the patients and fell in 22 (37%) patients from the initial to the second test. The absolute magnitude of changes over time averaged 7 mm for EDD, 125 g for mass, and 6 mL/kg per minute for peak Vo(2). Changes in LV size and mass per year were significantly related to those in peak Vo(2) (r = -0.49 for EDD, r = -0.56 for ESD, and r = -0.44 for LV mass, respectively, all P <.001) and ventilatory response to exercise (r = 0.60, r = 0.58, and r = 0.72 for EDD, ESD, and LV mass; respectively, all P <.001). CONCLUSIONS: Changes over time in objective measures of LV dimensions and mass, in patients with CHF are significantly related to those in exercise capacity and respiratory efficiency.

Valve replacement for aortic stenosis in patients with poor left ventricular function: comparison of early changes with stented and stentless valves.

BACKGROUND: Long-standing aortic stenosis causes significant left ventricular (LV) dysfunction, which may progress irreversibly. In many cases, LV function can be salvaged by aortic valve surgery, although debate exists regarding the best valve prosthesis to use. METHODS AND RESULTS: We studied 33 patients retrospectively who had significant aortic stenosis and impaired LV systolic function, as assessed by transthoracic Doppler echocardiography. Patients were assessed preoperatively and before discharge from the hospital. A total of 20 patients received a stentless (homograft or Toronto) valve, and 13, a stented valve. No patient had significant aortic regurgitation or other valvular disease. Preoperatively, fractional shortening was 18.8+/-5.5% in the stentless group and 18.6+/-3.8% in the stented group. Postoperatively, it was 25.6+/-6.9% (P<0.001 compared with baseline) and 17.0+/-2.8%, respectively (P<0.001 compared with stentless group). Fractional shortening improved because of a reduction in LV end-systolic and end-diastolic dimensions in the stentless group. Systolic long axis function at the LV free wall also recovered, with an increase in systolic excursion and both peak shortening and lengthening rates. No change was noted in mitral valve Doppler patterns. CONCLUSIONS: Patients who received a stentless valve demonstrated a significantly greater early improvement in LV systolic function compared with those who received a stented valve.

Right ventricular function after pulmonary autograft replacement of the aortic valve.

BACKGROUND: The pulmonary autograft operation (the Ross procedure) involves excision of a portion of the right ventricular (RV) outflow tract, prolonged cross-clamp times, and insertion of a pulmonary homograft. There is concern about the effect of such operations on right ventricular function. METHODS AND RESULTS: Twenty-five patients undergoing either pulmonary autograft or homograft replacement of the aortic valve as part of a prospective randomized trial had echocardiographic RV long-axis measurements performed before surgery and 6 months (range 3 to 12 months) after surgery. In all patients, systolic excursion (SE) and both shortening and lengthening rates (SR and LR, respectively) were reduced postoperatively (P<0.05) (homografts: SE 1.5+/-0.4 versus 2.3+/-0.6 cm, SR 6.8+/-2.1 versus 9. 6+/-3.1 cm/s, LR 6.0+/-1.8 versus 8.9+/-3.0 cm/s; autografts: SE 1. 4+/-0.4 versus 2.2+/-0.4 cm, SR 5.8+/-3.0 versus 8.2+/-3.0 cm/s, LR 5.7+/-1.9 versus 8.5+/-3.7 cm/s). There were no differences between the 2 groups. Eighteen patients who had undergone either aortic homograft or pulmonary autograft surgery were studied between 6 and 35 months after surgery. RV volumes were assessed with the use of MRI in addition to echocardiographic RV long-axis measurements. Global volumes were increased to a similar amount in both groups (homografts: end-diastolic volume 145+/-34 mL, end-systolic volume 78+/-23 mL; autografts: end-diastolic volume 157+/-33 mL, end-systolic volume 89+/-25 mL; P=NS), whereas stroke volumes were maintained in both groups (homografts 67+/-15 mL, autografts 67+/-16 mL; P=NS). RV SE was depressed in both groups to a similar degree to that seen with the previous group (homografts 1.5+/-0.3 cm, autografts 1.4+/-0.2 cm). CONCLUSIONS: Aortic valve replacement with either a pulmonary autograft or an aortic homograft leads to a degree of persistent RV longitudinal dysfunction that is not more pronounced in those undergoing the Ross procedure. The mechanisms and long-term effects of these changes must be further studied.

The effects of cardioplegia on coronary pressure-flow velocity relationships during aortic valve replacement.

OBJECTIVE: The acute physiological response of the coronary circulation to aortic valve replacement (AVR) has not been fully elucidated. This study aimed to characterize the changes in coronary perfusion pressure-flow velocity relationships, and to test whether this relationship is affected by cardioplegic method. METHODS: Nineteen patients (mean age 67 +/- 12 (SD) years, 9 males) undergoing aortic valve replacement who received either cold blood cardioplegia (CBC, n = 9) or warm blood cardioplegia (WBC, n = 10), were prospectively studied before and 30 min after the operation, using transesophageal Doppler echocardiography combined with high fidelity left ventricular (LV) and aortic pressures. We thus determined: (1) Diastolic flow velocities in proximal anterior descending coronary artery (LAD), and simultaneous aorta to LV pressure differences. (2) The slope (LAD proximal linear resistance) and pressure intercept (zero flow pressure) of this relationship. (3) Overall LAD linear resistance as the ratio of mean diastolic flow velocity to mean pressure difference between aorta and left ventricle. (4) LV myocardial stroke work. RESULTS: Following operation, myocardial stroke work fell from 5.2 +/- 2.7 to 3.0 +/- 1.7, mJ cm(-3) (P = 0.001), LAD mean diastolic flow velocity increased from 47 +/- 19 to 74 +/- 21, cm s(-1) (P = 0.0002). LAD overall linear resistance fell (0.75 +/- 0.24 vs. 1.26 +/- 0.26, mmHg cm(-1) s, P = 0.001). LAD proximal linear resistance, however, remained unchanged (P = 0.21), but the zero flow pressure fell (18 +/- 12.6 vs. 27 +/- 12.2, mmHg above LV end diastolic pressure, P = 0.013). With similar fall in myocardial work postoperatively, there was a greater fall in zero flow pressure after WBC than CBC (48 +/- 28 vs. 19 +/- 13,% of pre-op, P = 0.012), and a greater increase in flow velocity time integral (127 +/- 81 vs. 53 +/- 59,%, P = 0.039). CONCLUSION: Instantaneous diastolic LAD pressure-flow velocity relations in the early postoperative period can be explained more satisfactorily in terms of zero flow pressure and proximal linear resistance than simple resistance alone. The fall in zero flow pressure alone explains the increase in LAD flow velocity immediately after aortic valve replacement. The extent of this fall is greater after warm rather than cold blood cardioplegia.

How high can a correlation coefficient be? Effects of limited reproducibility of common cardiological measures.

In clinical studies the linear correlation coefficient is commonly used to quantify the strength of the association between two variables, such as height and weight: the value of r indicates whether the relationship is a strong one. However, actual clinical data includes an underlying physical variable plus an inevitable measurement error component that represents the reproducibility of the test used. If test reproducibility is poor, then even if the underlying physical variables are perfectly correlated, the actual observed correlation coefficient cannot be one but must be somewhat less. We present a method for calculating the reduction in correlation coefficient due to limited reproducibility, and discuss its implications with respect to experimental design and interpretation.