Page 13 - Journal of Structural Heart Disease Volume 3, Issue 3

Review Article
66
c) Post-Ross procedure (pulmonary autograft)
a) Post arterial switch/Rastelli in transposition of
the great arteries
b) Post left ventricle to pulmonary artery conduit
in congenitally corrected transposition
c) Any dysfunctional conduit/tissue valve between
ventricle and pulmonary artery
General Criteria
There are no strict rules with respect to patient’s age and weight, but as a guide, patients should be older than six years and weigh more than 25 kg as the delivery systems are still bulky.
It is essential for the entry veins to be of adequate size, that is, around 6 mm or more. Ultrasound eval- uation of these is usually su cient. Arterial access from the femoral or radial arteries is required to assess the coronary arteries during balloon interro- gation of the RVOT.
There are some situations where percutane- ous pulmonary valve implantation should not be considered:
a)If the coronary arteries are compromised or within 5 mm of the interrogating balloon
b) If the landing zone is too large for the available valve sizes; for non-stenosed out ow tracts, the valve size should be 10–15% larger to ensure anchorage and stability
c) Infection within the previous 6 months which includes systemic infection or endocarditis
Speci c Observations/Investigations
Evaluation consists of clinical assessment as well as supportive investigations.
The ECG may show a broad, complex, right bundle branch block; if the QRS is wider than 180 msec, this usually implies signi cant right ventricular volume overload with arrhythmogenic tendencies although in many the QRS width is closer to 160 msec when oth- er indications already exist. Holter monitoring is part of the work-up and the presence of ventricular tachy- cardia may be an indication for intervention although there are several mechanisms apart from mechanical right ventricular dysfunction. In general, however, the mechanical component is addressed rst followed by
electrophysiology if ventricular tachycardia persists following haemodynamic optimization.
A cardio-pulmonary exercise test (CPEX) pro- vides quantitative workload capacity and is useful to demonstrate any progression over a period of obser- vation and this helps to optimize the timing for inter- vention as well as to observe any bene ts following intervention.
The echocardiogram/Doppler is the common- est investigation carried out to evaluate the RVOT obstruction as well as the e ect of obstruction and regurgitation on the right ventricle. It provides infor- mation about the proximal pulmonary arteries, the velocity across the RVOT, the degree of pulmonary re- gurgitation, as well as the velocity and regurgitation of the tricuspid valve to estimate the right ventricu- lar pressure and observe the degree of regurgitation. Transesophageal echocardiography is sometimes used during pulmonary valve implantation and may help with identifying the landing zone, but the valve lea ets are not easily seen due to scatter from the frame and if there is a suspicion of valve dysfunction, intra-cardiac echocardiography (ICE) is superior.
More speci c and objective information is obtained on MRI/CT. These provide details of the RVOT including the diameter and length, spatial orientation of pulmo- nary an coronary arteries, quantitative RVOT obstruction and regurgitation, right ventricular function, and the right ventricular end diastolic volume correlated to body surface area. A right ventricular end diastolic volume of greater than 150 cc/m2 is considered signi cant, as are an end systolic volume of more than 90 cc/m2, a regurgitant fraction of more than 35% and an RV ejection fraction of less than 40%. MRI is superior particularly for quantitative observations and these are important to assess progres- sion but some patients with implantable devices, such as pacemaker/de brillators are only suitable for CT.
Angiography and direct hemodynamic assessment can be done during the pulmonary valve implantation but increasingly this is carried out in advance during which balloon interrogation of the RVOT is carried out for more accurate measurement and to assess wheth- er the coronary arteries could be compromised with stenting and/or valve implantation. If the balloon in- terrogation proves safe, the RVOT can be stented at the same time and for the pulmonary valve to be im- planted a few months later. A gap between these pro-
Journal of Structural Heart Disease, [Month Year]
Volume 3, Issue 3:62-72