Intramural aortic haematoma causing ischaemia of the spinal cord

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Impaired matching of perfusion and ventilation in heart failure detected by 133xenon

In severe chronic heart failure (CHF) the ventilatory cost of CO2 elimination during exercise (VE/VCO2) is increased, suggesting ventilation/perfusion (V/Q) mismatch. The relationship of exercise VE/VCO2 regression slope m to deadspace ventilation was studied in 15 patients with CHF who underwent cardiopulmonary exercise testing and arterial blood gas monitoring. Regional lung ventilation and perfusion was studied, using 133xenon, at rest and peak exercise in a further group of 10 CHF patients and in five normal subjects. VE/VCO2 slope m correlated well with deadspace ventilation at peak exercise in the 15 patients with CHF. We therefore used exercise VE/VCO2 slope m to categorize CHF patients undergoing 133xenon imaging into groups with increased (slope m > 36) or normal (slope m < 36) exercise deadspace ventilation. In normals, resting V/Q determined by 133xenon showed a gravitational gradient, which improved on exercise as a result of relative increases and of relative reductions in regional perfusion; no significant changes in regional ventilation distribution were detected. In patients with CHF who had normal slope m (n = 5), rest and exercise V/Q were similar to the normal subjects. In CHF patients with increased slope m (n = 5) however, the resting gravitational gradient of V/Q was lost, and there were no significant changes in relative perfusion distribution on exercise. These findings suggest that the increased ventilatory cost of CO2 elimination found in certain patients with CHF is related to inability to coordinate and optimise the relative distribution of lung perfusion with respect to ventilation during exercise.

Valvular heart disease: recommendations for investigation and management. Summary of guidelines produced by a working group of the British Cardiac Society and the Research Unit of the Royal College of Physicians

Despite the decline of rheumatic fever, valvular heart disease remains a common and important problem. The investigation and treatment of patients have been revolutionised by the widespread availability of echocardiography, which provides information about disease aetiology, accurate and non-invasive assessment of severity and a means of monitoring progression. These advances have facilitated progress in reconstructive valve surgery and the application of balloon valvuloplasty. Improved valve prostheses and reduction in peri-operative mortality have also broadened the indications for valve replacement surgery. A working party convened by the British Cardiac Society and the Royal College of Physicians of London have reviewed current practice and provided guidelines, summarised in this article, for the investigation and management of adults with valvular heart disease in primary care, district general hospitals and tertiary referral centres.

Time-related hemodynamic changes after aortic replacement with the freestyle stentless xenograft

BACKGROUND

The Freestyle valve is a porcine aortic root fixed with net zero pressure across the cusps and treated with the anticalcification agent alpha-aminooleic acid. We evaluated the hemodynamic function of this stentless valve.

METHODS

We implanted the valve into 80 consecutive patients scheduled to receive a bioprosthesis. Sixty-nine patients were more than 70 years old and 14 had calcified aortic sinuses. The "cylinder within a cylinder" implantation technique was used. Twenty-seven patients received coronary grafts, and 3 had mitral repair. All patients were studied echocardiographically during week 1 and 41 were studied at 6 months.

RESULTS

Median ischemic time for isolated aortic valve replacement was 44 minutes. There were four hospital deaths, none valve related. No patient had more than trivial aortic regurgitation. Mean systolic gradients for valve sizes 21 to 25 mm fell significantly with time (p < or = 0.05) due to remodeling of the porcine root and early regression of left ventricular hypertrophy. Late hemodynamic function was equivalent to an aortic homograft.

CONCLUSIONS

The Freestyle valve is easily implanted and has excellent hemodynamics. Transvalvular gradients decrease progressively.

Exercise ventilation after balloon dilatation of the mitral valve

BACKGROUND

Exertional dyspnoea is a limiting symptom in many patients with mitral stenosis but its causes remain incompletely understood. Ventilation during exercise is abnormal in chronic heart failure of all causes and there is increased ventilatory cost of carbon dioxide production.

PATIENTS

23 patients with rheumatic mitral stenosis undergoing percutaneous balloon dilatation of the mitral valve were studied to investigate exercise ventilation.

METHODS

Treadmill exercise tests with respiratory gas analysis were performed before and 1 day, 7 days, and 10 weeks after balloon dilatation of the mitral valve. The relation between ventilation (VE) and production (VCO2) was analysed by linear regression.

RESULTS

The VE/VCO2 slope was linear in all patients and before balloon dilatation of the mitral valve it correlated inversely with peak minute oxygen consumption (VO2) (rs = -0.47, P < 0.05), exercise duration (rs = -0.66, P < 0.01), and mitral valve area (rs = -0.5, P < 0.05). The VE/VCO2 slope declined acutely after balloon dilatation of the mitral valve (n = 10) (mean (SD) 41 (4) v 36 (2.9), P < 0.05) and did not change again thereafter. At 10 weeks (n = 23) exercise duration (460 (230) v 630 (240) s, P < 0.01) and peak VO2 (12.7 (4.3) v 14.9 (4.8) ml/kg/min, P < 0.05) increased significantly.

CONCLUSIONS

Patients with rheumatic mitral stenosis have a similar increase in the VE/VCO2 slope to that of patients with heart failure from other causes. Successful balloon dilatation of the mitral valve is associated with an acute reduction in the exercise VE/VCO2 slope.

Can an echocardiographic score predict who will benefit clinically from balloon dilation of the mitral valve?

Deciding whether a patient with sub-optimal mitral valve anatomy will benefit from percutaneous mitral valvotomy remains a demanding clinical problem. We assessed the ability of an established echo score applied to transoesophageal images to predict absolute increases in mitral valve area and improvement in exercise capacity. Twenty five consecutive patients undergoing routine percutaneous mitral valvotomy were studied. Changes in exercise tolerance were measured by serial cardiorespiratory treadmill exercise testing. Before the procedure, exercise duration was directly related to mitral valve area (rs = 0.44, P < 0.05). Following percutaneous mitral valvotomy there was an increase in valve area (0.9 +/- 0.2 to 1.4 +/- 0.3 cm2, P < 0.0001) and repeat exercise testing demonstrated increases in exercise duration (470 +/- 220 to 610 +/- 240 s, P < 0.001) and peak VO2 (12.6 +/- 4.2 to 15.1 +/- 4.5 ml/kg/min, P < 0.01). There was an inverse correlation between the echo score and the increase in valve area (rs = -0.52, P < 0.05) but no relationship between the echo score and the increase in exercise duration or peak minute oxygen consumption (VO2). These data demonstrate that a score applied to transoesophageal images echocardiographic images can predict changes in mitral valve area but that the score fails to predict functional improvement for an individual patient. This suggests, therefore, that patients without contraindications to valvotomy whose valves have a high echo score should still be considered for valvotomy as they may benefit considerably from the procedure.

Kinetics of smooth muscle cell proliferation and intimal thickening in a pig carotid model of balloon injury

Restenosis as a result of neointimal smooth muscle cell accumulation is an important limitation to the effectiveness of balloon angioplasty as a treatment for end-stage atherosclerosis. Quantitative animal models allow the definition of pathophysiological mechanisms and the evaluation of new therapeutic strategies. In this study we quantified the time course of neointima formation by morphometry, and smooth muscle cell (SMC) proliferation by immunocytochemistry for proliferating cell nuclear antigen (PCNA), in the pig carotid artery 0-28 days following balloon injury. This led to two distinct kinds of injury observed also in clinical studies, namely medial dilatation or deep medial tearing with rupture of the internal elastic lamina. Dilatation injury alone led to medial enlargement and neointima formation by 7 days, which did not increase further up to 28 days. Medial enlargement was similar following rupture of the internal elastic lamina; however the sum of neointima formation plus the area of medial repair ('neomedia') increased progressively up to 21 days after balloon injury. Balloon injury increased the PCNA index of smooth muscle cells in the media underlying an intact internal elastic lamina maximally after 3 days. The PCNA index in the neointima and especially in the neomedia was greater and maximal after 7 days. Endothelial regrowth occurred by 21 days in the presence or absence of medial tears. Our results establish a quantitative pig model of balloon injury which will allow the assessment of new therapeutic strategies directed at two clinically relevant types of injury. Medial tearing is associated with an enhanced and localized proliferative response and may therefore be especially important in human restenosis.

The effects of exogenous nitric oxide on smooth muscle cell proliferation following porcine carotid angioplasty

OBJECTIVES

Nitric oxide reduces platelet adhesion and platelet-thrombus formation following angioplasty and inhibits smooth muscle cell (SMC) proliferation in vitro. In this study we investigated the effects of the nitric oxide donor molsidomine on SMC proliferation and intimal growth following experimental angioplasty.

METHODS

Bilateral carotid angioplasty was performed in 24 anesthetized pigs. Animals were randomized to receive oral molsidomine (whose active metabolite is SIN-1; 0.3 mg/kg every 8 h; n = 12) or placebo (n = 12) for 48 h before angioplasty and until the arteries were removed either 7 or 21 days (n = 12 each group) later. SMC proliferation was quantified by immunocytochemical staining with an antibody to the proliferating cell nuclear antigen (PCNA) and morphometric changes by computerized planimetry. SMC's were identified by alpha-actin staining.

RESULTS

After 3 weeks treatment with molsidomine there was a significant prolongation in bleeding time [mean +/- SEM] (151 +/- 6 to 187 +/- 7 s. P < 0.01) and a sustained increase in arterial wall cyclic GMP (6.57 +/- 1.29 to 13.24 +/- 1.02 pmol/mg protein, P < 0.05). Molsidomine significantly reduced intimal proliferation when compared with placebo in arteries with an intact internal elastic lamina at 7 days (4.3 +/- 0.7 vs. 9.6 +/- 1.9 PCNA index, P < 0.005) and medial proliferation at 7 days (2.4 +/- 0.2 vs. 4.2 +/- 0.7 PCNA index, P < 0.05) and at 21 days (1.3 +/- 0.1 vs. 1.9 +/- 0.2 PCNA index, P < 0.05) after angioplasty. In arteries with rupture of the internal elastic lamina, intimal and medial SMC proliferation were similar in molsidomine- and placebo-treated animals. Intimal cell number and intimal area were uninfluenced by treatment with molsidomine in either the presence or absence of rupture of the internal elastic lamina.

CONCLUSIONS

These results show for the first time that exogenous nitric oxide inhibits SMC proliferation following balloon angioplasty in vivo. The antiproliferative effects of nitric oxide are overwhelmed when injury is severe and are not associated with a reduction in intimal thickening. The inhibitory effects of nitric oxide on platelet adhesion and SMC proliferation identify a possible role for high local concentrations of nitric oxide to modify the vascular response to balloon angioplasty.

Perfusion/ventilation mismatch during exercise in chronic heart failure: an investigation of circulatory determinants

BACKGROUND

The ventilatory cost of carbon dioxide (CO2) elimination on exercise (VE/VCO2) is increased in chronic heart failure (CHF). This reflects increased physiological dead space ventilation secondary to mismatching between perfusion and ventilation during exercise. The objectives of this study were to investigate the relation of this increased VE/VCO2 slope to the syndrome of CHF or to limitation of the exercise related increase of pulmonary blood flow, or both.

PATIENTS AND METHODS

Maximal treadmill exercise tests with respiratory gas analysis were performed in 45 patients with CHF (defined as resting left ventricular ejection fraction < 40% on radionuclide scan); 15 normal controls; 23 patients with coronary artery disease and normal resting left ventricular function; and 13 pacemaker dependent patients (six with and seven without CHF) directly comparing exercise responses in rate responsive and fixed rate mode.

RESULTS

Patients with CHF had a steeper VE/VCO2 slope than normal controls: this was related inversely to peak VO2 below 20 mol/min/kg. In patients with coronary artery disease in whom peak VO2 (at respiratory exchange ratio > 1) was as limited as in the patients with CHF but resting left ventricular function was normal, the VE/VCO2 slope was normal. In pacemaker dependent patients fixed rate pacing resulted in lower exercise capacity and peak VO2 than rate responsive pacing; the VE/VCO2 slope was normal in patients without CHF but steeper than normal in patients with CHF; the VE/VCO2 slope was steeper during fixed rate than during rate responsive pacing in these patients with CHF.

CONCLUSIONS

These findings suggest that the perfusion/ventilation mismatch during exercise in CHF is related to the chronic consequences of the syndrome and not directly to limitation of exercise related pulmonary flow. Only when the syndrome of CHF is present can matching between perfusion and ventilation be acutely influenced by changes in pulmonary flow.

Transoesophageal echocardiography as the sole diagnostic investigation in patients with suspected thoracic aortic dissection

OBJECTIVES

To assess the value and limitations of using transoesophageal echocardiography as the sole diagnostic test in patients with suspected thoracic aortic dissection.

DESIGN

Retrospective data review over a two year period.

SETTING

A regional cardiothoracic centre.

PATIENTS

Data were compiled from admission records, surgical records, and lists of patients undergoing diagnostic investigations in the hospital. Patient's notes were used to identify presentation, management, and outcome.

INTERVENTIONS

Patients were managed according to the policy of our unit, which is to treat patients with dissection affecting the ascending aorta by an operation. Patients with uncomplicated dissection sparing the ascending aorta are initially managed medically.

MAIN OUTCOME MEASURES

In hospital and two year follow-up of patients who were investigated by transoesophageal echocardiography alone.

RESULTS

Of 48 patients referred, 45 underwent transoesophageal echocardiography. Dissection was confirmed in 22 patients. Transoesophageal echocardiography showed the proximal extent of the dissection in 21/22 (96%) and only one patient required a further diagnostic investigation. Ten patients with dissection of the ascending aorta underwent graft replacement of the ascending aorta; operative mortality was 10% and their two year survival was 80%. Of the eight patients with dissection of the descending aorta, six were discharged home, and five were alive at two years. No patient without evidence of dissection on their initial transoesophageal echocardiographic examination required re-investigation into possible dissection in the two years after discharge.

CONCLUSIONS

In patients with suspected thoracic dissection transoesophageal echocardiography rapidly and safely gives all the necessary diagnostic information. Further investigations, including coronary angiography, before surgery are unnecessary.

Abnormalities of left ventricular flow following mitral valve replacement: a colour flow Doppler study

Left ventricular flow patterns were studied at rest by colour flow Doppler echocardiography in 33 patients with mitral tilting-disc prostheses (group 1), in 38 patients with mitral tissue prostheses (group 2) and in 18 healthy volunteers (controls). A 'crossed' flow pattern was seen in 14 patients with mechanical (42%) and in 15 patients with tissue prostheses (39%). The remaining patients and all controls had either 'parallel' or 'intermediate' flow patterns which were classified as 'normal'. There was a significant correlation between the type of flow pattern and the position of the mitral prosthesis in both study groups. The presence of a crossed flow pattern, however, was not related to functional status (assessed clinically by NYHA class) or to abnormalities on the electrocardiogram. Left atrial size was greater in patients with crossed flow than in those without, but all other echocardiographic parameters were similar. Eight patients with crossed and eight with normal flow patterns underwent treadmill exercise testing; there was no difference between the two groups with regard to exercise performance as determined by exercise duration, maximum oxygen consumption and the ventilatory response to exercise. The results of this study indicate that the pattern of blood flow within the left ventricle may be fundamentally altered by the orientation of both mechanical and tissue prostheses. The presence of a crossed flow pattern is not, however, accompanied by significant deleterious haemodynamic or functional consequences.

Role of balloon dilatation of the aortic valve in pregnant patients with severe aortic stenosis

The outcome of unrelieved severe symptomatic aortic stenosis in pregnancy is poor. Though the valve lesion can be corrected surgically before delivery at a low risk to the mother, cardiopulmonary bypass during pregnancy carries a high risk to the fetus. Two patients in the second trimester of pregnancy were successfully managed with balloon dilatation of the aortic valve. Both delivered healthy infants and were well a year later. Balloon dilatation of the aortic valve is a useful palliative procedure in the management of pregnant women with severe aortic stenosis.