Ventricular stroke work loss: validation of a method of quantifying the severity of aortic stenosis and derivation of an orifice formula.

Because aortic stenosis results in the loss of left ventricular stroke work (due to resistance to flow through the valve and turbulence in the aorta), the percentage of stroke work that is lost may reflect the severity of stenosis. This index can be calculated from pressure data alone. The relation between percent stroke work loss and anatomic aortic valve orifice area (measured by planimetry from videotape) was investigated in a pulsatile flow model. Thirteen valves were studied (nine human aortic valves obtained at necropsy and four bioprosthetic valves) at stroke volumes of 40 to 100 ml, giving 57 data points. Valve area ranged from 0.3 to 2.8 cm2 and mean systolic pressure gradient from 3 to 84 mm Hg. Percent stroke work loss, calculated as mean systolic pressure gradient divided by mean ventricular systolic pressure x 100%, ranged from 7 to 68%. It was closely related to anatomic orifice area with an inverse exponential relation and was not significantly related to flow (r = -0.15). An orifice formula was derived that predicted anatomic orifice area with a 95% confidence interval of +/- 0.5 cm2 (orifice area [cm2] = 4.82 [2.39 x log percent stroke work loss], r = -0.94, SEE = 0.029). These results support the clinical use of percent stroke work loss as an easily obtained index of the severity of aortic stenosis.

Efficacy of aortic balloon valvoplasty: direct measurement of orificial area in a model with pulsatile flow.

The efficacy of balloon valvoplasty of calcific aortic stenosis remains controversial. We studied, therefore, 5 human aortic valves obtained at necropsy in a positive-displacement pulse duplicator which delivered stroke volumes of 40-100 ml with a quasiphysiological waveform of flow. All valves had three leaflets without commissural fusion and were preserved in antibiotic solution before study. Orificial area was planimetered from videotape of opening of the valve and varied with flow in all cases. Valvoplasty with a 20 mm diameter balloon had no effect on the orifice of the normal valve but increased the orifice of 2 mildly calcified valves from 0.70-1.77 cm2 (range) at baseline to 1.06-1.95 cm2. In 2 valves with severe calcification of the leaflets, the orifice was increased from 0.31-0.82 cm2 to 0.73-1.07 cm2. Dual balloon valvoplasty achieved a variable but small further increase in orificial area. No valve showed tears of the leaflets or fracture of calcific deposits after valvoplasty. We conclude that balloon valvoplasty can acutely increase orificial area, independently of any change in stroke volume. In valves without commissural fusion, its mechanism appears to be an increase in the pliability of the leaflets which does not require macroscopic fracture of calcific deposits.

Coronary arteriography in a district general hospital: feasibility, safety, and diagnostic accuracy.

OBJECTIVE: To determine the feasibility, safety, and diagnostic accuracy of coronary arteriography in the radiology department of a district general hospital using conventional fluoroscopy and videotape recording. DESIGN: Observational study of the feasibility and safety of coronary arteriography in a district general hospital and analysis of its diagnostic accuracy by prospective within patient comparison of the video recordings with cinearteriograms obtained in a catheter laboratory. SETTING: Radiology department of a district general hospital and the catheter laboratory of a cardiological referral centre. SUBJECTS: 50 Patients with acute myocardial infarction treated with streptokinase who underwent coronary arteriography in a district general hospital three (two to five) days after admission. 45 Of these patients had repeat coronary arteriography after four (three to seven) days in the catheter laboratory of a cardiological referral centre. MAIN OUTCOME MEASURES: Incidence of complications associated with catheterisation and the sensitivity and specificity of video recordings in the district general hospital (judged by two experienced observers) for identifying the location and severity of coronary stenoses. RESULTS: Coronary arteriograms recorded on videotape in the district general hospital were obtained in 47 cases and apart from one episode of ventricular fibrilation (treated successfully by cardioversion) there were no complications of the procedure. 45 Patients were transferred for investigation in the catheter laboratory, providing 45 paired coronary arteriograms recorded on videotape and cine film. The specificity of the video recordings for identifying the location and severity of coronary stenoses was over 90%. Sensitivity, however, was lower and for one observer fell below 40% for lesions in the circumflex artery. A cardiothoracic surgeon judged that only nine of the 47 video recordings were adequate for assessing revascularisation requirements. CONCLUSIONS: Coronary arteriography in the radiology department of a district general hospital is safe and feasible. Nevertheless, the quality of image with conventional fluoroscopy and video film is inadequate and will need to be improved before coronary arteriography in this setting can be recommended.

Balloon dilatation of the aortic valve for inoperable aortic stenosis.

The place of balloon dilatation of the aortic valve in the treatment of calcific aortic stenosis is controversial. Thirty two patients (mean age 76) in whom valve replacement was contraindicated were followed up for three to 24 months (mean 8); 25 were in functional class III or IV according to the New York Heart Association's classification. Major complications of the procedure occurred in four patients. Echocardiography and Doppler studies were performed before operation and before discharge in 28 patients, and the area of the valve was measured again six to 50 (mean 23) weeks after operation in 11 patients. The peak to peak aortic pressure gradient fell from a mean of 65 (SD 24) to 46 (20) mm Hg, but the area of the aortic valve, measured by Doppler echocardiography, in 18 patients showed a modest but significant increase, from 0.61 (0.16) to 0.74 (0.23) cm2. One month after dilatation, 29 patients were alive, of whom 17 had improved symptoms. Only two had lasting clinical benefit. Sixteen patients died, 12 of a cardiac cause. The estimated one year survival rate was 49%. Six patients underwent or required valve replacement because of persisting symptoms. In view of its limited long term efficacy balloon dilatation of the aortic valve should be used only for patients with severe symptoms whose life expectancy is limited by other disease or who are considered to be unsuitable for valve replacement. It may have a role in improving the condition of patients who present with cardiogenic shock or pulmonary oedema before valve replacement is undertaken.

Abnormal diastolic function in patients with type 1 diabetes and early nephropathy.

Left ventricular diastolic function was assessed by pulsed Doppler echocardiography in non-diabetic controls (n = 11) and in patients with type 1 diabetes without microvascular disease (n = 16; diabetic controls), with microalbuminuria (n = 9), or with early persistent proteinuria (n = 11). The peak filling velocities during the early and atrial phases of left ventricular diastole and their ratio (E:A ratio) were measured. All patients with diabetes had a normal serum concentration of creatinine and exercise electrocardiogram. The mean E:A ratio was significantly lower in those with proteinuria than in the diabetic controls because of an increase in peak atrial filling velocity; most patients with proteinuria had an abnormal E:A ratio of less than 1.0. Multiple regression analysis showed that systolic blood pressure was the major determinant of both the peak filling velocity during the atrial phase of diastole and also left ventricular mass. Blood pressures were significantly higher in the proteinuria group than in the diabetic controls. Glycaemic control and autonomic function did not influence diastolic filling. The slightly raised blood pressures at the earliest stages of diabetic nephropathy are sufficient to alter left ventricular diastolic compliance--this may reflect early hypertensive heart disease. These data do not preclude a specific heart muscle disease related to diabetes, but suggest that these slightly raised blood pressures contribute significantly to left ventricular dysfunction in these patients, in whom the risk of cardiovascular disease is already greatly increased.

QT prolongation on the electrocardiogram in diabetic autonomic neuropathy.

Patients with Type 1 diabetes and autonomic neuropathy have an increased risk of sudden death for which the mechanism remains obscure. Prolongation of the QT interval on the electrocardiogram may occur with sympathetic dysfunction and is also associated with ventricular arrhythmia and sudden death. We have therefore measured the QT interval in patients with Type 1 diabetes with normal, borderline, and definitely abnormal autonomic function tests and in non-diabetic control subjects. The maximum QT interval was measured on 12-lead electrocardiograms recorded at rest and then plotted against the RR interval. The QT interval was above the upper 95% limit for the non-diabetic control subjects in 5 diabetic patients with abnormal autonomic function tests (33%), but in no cases with normal or borderline tests. Multivariate analysis confirmed that autonomic score contributed significantly (p less than 0.025) to the variance in QT interval. The raw Valsalva ratio alone also contributed significantly to the variance in QT interval (p = 0.025). Heart rate variability, heart rate response to standing, age, sex, and the presence of symptoms of autonomic neuropathy did not contribute significantly.

Ambulatory electrocardiography: an open-access service for general practitioners.

Access to ambulatory electrocardiography would enable general practitioners to investigate certain patients with cardiac symptoms without the need for hospital referral. An analysis has been made of the results in 200 consecutive patients referred to a pilot open-access service based at three health centres. Twenty-two GPs used the service, although there was a wide range (1-48) in the number of patients each referred. In 72 patients aged under 50 years, abnormalities other than extrasystoles were detected in only six; major significant arrhythmias were found in three patients, although treatment was required in only one case. Arrhythmias were frequent in patients aged over 50 years but were usually minor; 16/128 (13 per cent) showed major significant arrhythmias. Pacemakers were implanted in two patients. Palpitation and/or dizziness were reported during the period of monitoring by 39 per cent of patients (and were equally common in both age groups), but in neither age group did these symptoms correlate with the occurrence of a significant arrhythmia. In primary care, palpitation and dizziness are rarely due to significant arrhythmias. To increase the cost-effectiveness of the service, ambulatory monitoring could be restricted to patients over 50 years of age, except when there is other evidence of heart disease.

Psychological and perceptual factors associated with arrhythmias and benign palpitations.

OBJECTIVE: Little is known about how patients who seek medical help for benign palpitations can be distinguished from those with clinically significant arrhythmias. This study tested whether patients with arrhythmia can be distinguished from those who are aware of sinus rhythm or extrasystoles on the basis of sex, prevalence of anxiety disorders, and heartbeat perception. METHODS: A consecutive sample of patients referred to a cardiology clinic participated in the study. Patients were diagnosed as having either arrhythmia (N = 62), extrasystoles (N = 75), or awareness of sinus rhythm (N = 47). They were assessed with use of the anxiety disorders and hypochondriasis modules of the Structured Clinical Interview for DSM-IV. Both patients and control subjects (N = 35) answered questionnaires measuring anxiety, fear of bodily sensations, and depression and underwent a heartbeat perception test. The present report focuses on patients who had palpitations but no comorbid cardiovascular disease. RESULTS: Patients with awareness of sinus rhythm could be distinguished from those with arrhythmia by several variables: female sex, higher prevalence of panic disorder, poor performance on the heartbeat perception test, report of palpitations when doing the test, higher heart rates, lower levels of physical activity, and (as trends) a greater prevalence of panic attacks, fear of bodily sensations, and depression. In contrast, patients with arrhythmias rarely reported palpitations when doing the test but were more likely to perceive their heartbeats accurately than patients with sinus rhythm and control subjects. Performance on the heartbeat perception test was intermediate in patients with extrasystoles; these patients also had an intermediate prevalence of panic disorder and intermediate depression scores. CONCLUSIONS: Measures of panic disorder and a simple heartbeat perception test could complement medical assessment in the diagnosis of patients who seek medical help for palpitations. The results also have implications for the treatment of patients with benign palpitations.

Regression of left ventricular hypertrophy with 1 year of antihypertensive treatment in type 1 diabetic patients with early nephropathy.

M-mode echocardiograms were recorded in 22 Type 1 diabetic patients with microalbuminuria (n = 10) or early persistent proteinuria (n = 12). Eight (36%) had both an increased left ventricular mass (males greater than 131 g m-2; females greater than 100 g m-2) and a systolic blood pressure above the 75th centile of the normal blood pressure distribution. These eight patients were treated with antihypertensive drugs, predominantly enalapril, for 1 year. Echocardiograms were repeated after 3 and 12 months. Systolic blood pressure at recruitment was 155 +/- 14 (+/- SD) mmHg, and was significantly lower after 3 months (146 +/- 12 mmHg; p less than 0.05) and 12 months (139 +/- 8 mmHg; p less than 0.005). Diastolic blood pressure did not change significantly. Both intraventricular septal width and left ventricular posterior wall thickness fell progressively and were significantly lower after 12 months treatment (15.0 +/- 2.7 vs 13.0 +/- 2.6 mm, and 10.3 +/- 1.9 vs 8.8 +/- 1.3 mm; both p less than 0.05). Left ventricular mass index was 148 +/- 29 g m-2 at recruitment, but lower after 3 months (131 +/- 25 g m-2; p less than 0.05) and 12 months (132 +/- 26 g m-2; p less than 0.005) antihypertensive therapy.

Continuity equation and Gorlin formula compared with directly observed orifice area in native and prosthetic aortic valves.

Orifice areas calculated by the continuity and Gorlin equations have been shown to correlate well in vivo. The continuity equation, however, gives underestimates compared with the Gorlin formula and it is not clear which is the more accurate. Both equations have therefore been tested against maximal orifice area measured by planimetry in eight prepared native aortic valves and four bioprostheses. A computer controlled, ventricular flow simulator (cycled at 70 beats/min) was used at five different stroke volumes that gave cardiac outputs of 2.8 to 7.0 l/min. The mean difference between measured and estimated orifice area was zero for the continuity equation, but -0.14 cm2 for the conventional Gorlin formula. Thus the Gorlin formula tended to give overestimates compared with both measured area and area estimated by the continuity equation, probably because of the effect of pressure recovery. When predictive equations derived from these data were tested, residual standard deviations were around 0.3 cm2 at all stroke volumes for the continuity equation, around 0.2 cm2 for the invasive Gorlin formula, and between 0.2 and 0.4 cm2 for the modified Gorlin formula. These results suggest that estimates of orifice area in an individual valve as judged by any of the equations tested should be seen as a guide to rather than as a precise measure of actual orific area.

Validation of the orifice formula for estimating effective heart valve opening area.

Interest in the Gorlin formula for estimating heart valve effective orifice area (EOA) has recently been rekindled and the formula itself has been challenged. In this validation study, explanted native heart valves, unimplanted mechanical prostheses, unimplanted bioprostheses and explanted bioprostheses have been tested in vitro in a pulsatile flow simulator. Pressures have been measured 30 mm upstream and 100 mm downstream from the plane of the valve sewing ring (to give pressure drop, pd in kPa). Flow (Q in 1 min-1) has been measured directly by electromagnetic flowmeter and orifice areas have either been taken from manufacturer supplied data (mechanical valves) or have been digitised from video images at maximum orifice (biological valves). The formula EOA = Q/(6.96 x pd 1/2) - 0.7 fitted the data with good correlation, r = 0.96 (n = 179). The orifice assumption on which this formula is based (cf. Gorlin formula) is confirmed though it is recommended that the formula should be modified to account for (i) the pressure recovery phenomenon and (ii) the fact that forward flow through a valve only occurs over a portion of the cycle in pulsatile flow. Heart rates used in the study ranged from 40 to 140 min-1, stroke volumes ranged from 20 to 114.3 ml, cardiac outputs from 2.0 to 8.0 1 min-1 and peripheral resistance from 0.1 to 1.6 kPa 1-1 min (1 - 12 mmHg l-1 min). Application of the formula was independent of the flow conditions.