11.12.3 Pulmonary stenosis

 

 

 

 The RV is strongly hypertrophied, sometimes dilated in failure; the RA is dilated (Figure 11.163).

 

The trunk of the PA is dilated beyond the stenosis. As it dilates, the RV becomes more like the LV: its flow becomes more dependent on preload but less dependent on afterload. The high pressure in the RV compresses the subendocardial layer, compromising coronary perfusion. It is therefore important to ensure adequate coronary perfusion by keeping systemic arterial pressure high (raising SAR with norepinephrine infusion). Positive pressure ventilation does not alter the performance of RV, which is determined by the pulmonary stenosis and not by the PAR distal to it.

Severe pulmonary stenosis is characterised by a thickened valve, rigid leaflets, calcifications and a dome-shaped deformation in systole. Vmax is > 4 m/s and maximum gradient > 64 mmHg. The RV is hypertrophied, including the RVOT, which is narrow. The trunk of the PA undergoes poststenotic dilatation [3].

 Figure 11.163: Pulmonary stenosis. A: Massive hypertrophy of the RV. B: Complex pulmonary stenosis in 90° midesophageal view by clockwise rotation of the probe from a 2-cavity view of the RV (case of adult tetralogy of Fallot). The right outflow tract is narrow and enlarged (arrow), the stenotic pulmonary valve is difficult to see in the proximal narrowing of the pulmonary artery; the RV is enlarged.

A ΔPmax ≥ 50 mmHg is a surgical indication for percutaneous valvulotomy or valve replacement [1]. The procedure involves replacement of the valve, usually with a biological valve conduit (homograft or heterograft) [3]. In a pulmonary homograft or heterograft, a maximum ΔP of up to 20 mmHg is tolerated in normal RV (Ross operation) and 30-40 mmHg in HRV (variable depending on preoperative gradient).

Video: Heterograft pulmonary valve replacement (Contegra).

The RV outflow tract is richer in with β receptors than the ventricular body. Its inotropic response to catecholaminergic stimulation is greater than that of the free wall and inflow tract. It can cause dynamic obstruction (right HOCM effect), which is common after pulmonary valve replacement for stenosis when the RV is very hypertrophied. Vmax in RVOT is 2-2.5 m/s, gradient > 20 mmHg [2]. Treatment consists of reducing catecholamines β , hypervolaemia, relative hypoventilation (increased PAR) and and β blockers (bolus esmolol).

 

Hemodynamics sought in pulmonary stenosis

High, stable right preload Systemic vasoconstriction RV afterload = fixed pulmonary stenosis, not PAR Well tolerated positive ventilation Normal rate, normocardia RV inotropic support (dobutamine, milrinone ± epinephrine) Full - normocardium - closed