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OUR MISSION: TO REDUCE THE BURDEN OF CARDIOVASCULAR DISEASE
Rafael Alonso-Gonzalez MD, MSc(1,2); Konstantinos Dimopoulos MD, MSc, PhD(1,2)
A 51 year old lady referred to our unit with increasing exertional dyspnoea for over a year. Her past medical history included human immunodeficiency virus (HIV) infection, stable on antiretroviral therapy, smoking history of 20 pack-years and moderate alcohol consumption. She complained of a progressive decline in her exercise tolerance from being previously unlimited to being able to walk less than 30 metres on the flat. Her chest radiograph showed cardiomegaly (cardiothoracic ratio (CTR) - 54%) due to dilated right heart chambers, a prominent main pulmonary artery and pruning of the peripheral pulmonary vessels (Figure 1).
Her echocardiogram performed at that time showed moderate mitral regurgitation due to prolapse of the posterior leaflet, a severely dilated right ventricle, mild tricuspid regurgitation with a peak velocity of 3.94 m/sec and also secundum atrial septal defect (1.8cm) with left to right shunt (videos 1 and 2)
Question 1: Does this patient have pulmonary arterial hypertension?
Correct answer: 4
Explanation of the answer:
A right heart catheterization, crossing the atrial septal defect, was performed showing moderate pulmonary arterial hypertension (mean PAP: 39 mmHg, left atrium pressure: 8 mmHg, PVR indexed: 12.6 WU x m2) with bidirectional shunt, predominantly left-to-right (Qp:Qs 1.5 l/min) (Figure 2).
Figure 2 – Right heart catheterization
Figure 2: All pressures are expressed in mmHg. Qp and Qs were calculated by Fick. Ao: aorta; mLA: mean left atrium pressure; mRA: mean right atrial pressure; PA: pulmonary artery; PVRi: indexed pulmonary vascular resistance; RV: right ventricle; Sat: oxygen saturation; SVRi: indexed systemic vascular resistance.
Question 2: Considering the right heart catheterization should we close the atrial septal defect?
Correct answer: 2
In this case,the possible aetiology of pulmonary hypertension is the ASD and/or the HIV infection. Although the defect is still shunting from left to right at rest, the PVR is already too high to consider closure at this point. Therefore, the patient should be considered for pulmonary vasodilators in view of the high PVRI. There is obvious right-to-left shunting on the catheter, which could be due to the high PVR but also due to the tricuspid regurgitation directing venous blood through the ASD to the left atrium. While high, the PVR does not appear to be at Eisenmenger (near systemic) levels.
The patient was started on sildenafil 20mg three times daily, with significant improvement in functional class (NYHA III to II) and exercise capacity. The 6-minute walking test (6MWT) increased to 330m.
The patient initially remained stable on single therapy,but approximately 2 years later she started to complain of increasing breathlessness and significant reduction of her exercise capacity reducing her 6MWT to 230m. Her transthoracic echocardiogram showed worsening of her mitral regurgitation (video 3). The right ventricle was severely dilated, but there was a persistent significant improvement in the eccentricity index since initiation of sildenafil. Her chest radiograph (figure 3) again showed cardiomegaly (CTR: 52%) due to dilated right chambers, dilated main pulmonary artery and signs of plethora (no pulmonary vascular pruning seen).
A cardiopulmonary exercise test was performed which showed a peak VO2 of 17 ml/kg/min, which is 68% of the predicted value, and a raised VE/VCO2 slope of 47 with good heart rate and blood pressure response.
Question 3: What should we do next?
Her exercise capacity is definitely worse, but it is difficult with the available data to identify the main reason for this deterioration. Therefore, we should neither increase the pulmonary vasodilator therapy nor refer the patient to surgery, before performing a right heart catheterization.
Right heart catheterization was performed showing significant reduction in PVR with increased left-to-right shunt (figure 4). Angiographically, there was moderate-to-severe mitral regurgitation and normal coronary arteries.
Figure 4: All pressures are expressed in mmHg. Qp and Qs were calculated by Fick. Ao: aorta; mLA: mean left atrium pressure; mRA: mean right atrial pressure; PA: pulmonary artery; PVRi: indexed pulmonary vascular resistance; RV: right ventricle; Sat: oxygen saturation; SVRi: indexed systemic vascular resistance.
Question 4: Considering the right heart catheterization,what should we do next?
Correct answer: 3
The management decision is not straightforward. The PVR is borderline whilst on sildenafil. Most of the rise in PA pressure is now explained by the increased pulmonary flow. Despite significant mitral regurgitation angiographically, the LA pressure is not raised as the ASD is acting as a relief valve, at the expense of more left-right shunt.
We felt that, in view of the relatively low PVR, the worsening of the mitral regurgitation to coincide with the worsening breathlessness, the stability of her HIV, she would benefit from mitral valve repair and repair of the ASD. As the PVR was not entirely normal we felt that closing the defect completely could promote right heart failure. Closure of the atrial septal defect with a fenestration can reduce the left to right shunt, whilst allowing a small communication to off-load the right ventricle, if needed.
The patient underwent mitral valve repair (annuloplasty using a Physio II 34mm ring and leaflet suturing at P1&P2), tricuspid valve annuloplasty (Contour 3D 36mm), ASD patch closure (Gore Tex patch with a 0.6 mm thick with 5mm fenestration), and right atrial cryoablation. During the perioperative period inotropic support and nitric oxide was administered for right heart failure, which responded promptly and she was successfully extubated after 48h and recovered very well.
She was reviewed a few months later and her exercise capacity improved significantly after the intervention. Her echocardiogram shows no signs of mitral regurgitation (video 4).
The management of patients with borderline haemodynamics is not straightforward. Current guidelines recommend using vasodilators and reassessing such patients for operability, even though no strong evidence exists for the “treat-and-repair” approach. In this case, there was a remarkable drop in PVR with only 20mg of sildenafil. The mitral regurgitation was significant and getting worse, causing lung congestion seen on the chest-X-ray and clinically, despite the ASD acting as a relief valve. By operating, we repaired both atrioventicular valves and reduced the shunt, while allowing a large enough fenestration to offload the right or left ventricle, as required. It is, in fact, not uncommon to see that left ventricles, which have been chronically “underfilled” due to the long-standing ASD, present with diastolic and possibly systolic dysfunction in the immediate postoperative period after ASD closure. This is usually transient, but in cases in which significant left ventricular diastolic or systolic dysfunction is present, closure with a fenestration is recommended.
While this patient had a satisfactory perioperative course and appears to be improving after her surgery, she will be monitored closely for progression of the pulmonary hypertension. She has been kept on sildenafil and we cannot predict whether the PVR will remain low, drop or increase over time.
Shunting through an atrial septal defect is influenced by numerous factors, including the size and location of the defect, the diastolic properties of the two ventricles, the presence and severity of pulmonary hypertension, the functional properties of the mitral and tricuspid valve etc. Therefore, the presence of right-to-left shunting does not necessarily imply that this is Eisenmenger syndrome (i.e. restrictive right ventricle or severe pulmonary stenosis). In a similar way, an increase in left-to-right shunt may occur with a stiffening of the left ventricle (with age or due to the development of diastolic dysfunction), worsening mitral regurgitation or mitral stenosis. In such cases, closing the defect without addressing the cause of the increase in shunting may lead to a sudden rise in LA pressure and pulmonary congestion. Full hemodynamic assessment and careful thought is essential before closing ASDs just “because we can”.
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