**8. Hypertrophic cardiomyopathy**

## **8.1. Pathophysiology and diagnosis**

risk of IE was 0.27 per 1000 person-years and for patient with aortic valve replacement (AVR), follow-up rate of IE was 1.53 per 1000 person-years [55]. In a different study, the cumulative risk was 13.3% out to 25 years post-surgery (median age of surgery 7.0 years) in patients where follow-up was available. This equates to a higher annualised incidence of 7.2 per 1000

Pulmonary stenosis (PS) is usually related to congenital valve stenosis, sometimes in association with genetic syndromes. Pulmonary regurgitation (PR) due to congenital disease is mostly seen following previous repair of ToF or valvotomy [62]. Endocarditis of the PV is relatively uncommon both pre and post-surgery [55, 57, 60], except in palliative shunts [60]. In PS, a rate of 0.09 per 1000 person-years has been reported [55]. Tetralogy of Fallot carries a

In the Kuijpers et al. study [5], the following were noted: (i) 8 cases of IE with closed ASD, but of those, 6/8 were associated with a valve abnormality; (ii) 13 cases of IE with VSD, where 9/13 were open, and (iii) no cases of IE with PDA (83.6% were closed). A large population-based registry study of children who underwent surgical repair of congenital heart lesions reported no patient developed IE after surgical repair of PDA (620 patients, median age 2.6 years) and likewise in an ACHD population, no IE was reported [58]. The annualised risk of IE post repair of AoC has been estimated at 1.2 per 1000 patient-years [60]. Very uncommonly, early (<6 months) IE occurs after closure. Late onset IE is very rare and is usually due to delayed endothelialisation [63–65]. In fact, in a surgical follow-up study by Morris et al. [60], no children who underwent repair of an isolated secundum ASD developed IE following surgery. Small numbers were seen with primum ASD and complete AVSD. After 6 months post-surgical closure of ASD, VSD and PDA, the risk of IE is virtually eliminated. The same holds true for transcatheter closure, although with residual defects, the risk is not eliminated [52]. After definitive surgical repair of ToF, the risk is estimated at 0.7 per 1000 patient years but is much

In a study by Rushani et al. [50], from the age of 0–6 months, unoperated cyanotic disease had an adjusted rate ratio (using ASD as a reference) for IE of 7.56, compared with the operated group at 9.22. For unoperated left-sided cardiac lesions, the rate ratio of IE was 2.35, though

In one study, the risk of IE was 5x increased early (<6 months) after any cardiac surgery in children [50] and 9.07x increased in adults up to 6 months after any non-valvular cardiac surgery [51]. Kuijpers et al. [5] reported valved-prosthetics in ACHD carry a hazard ratio (HR) of 17.29 (at 6 months), 15.91 (6-12 months) and 5.26 (>12 months) post-surgery. Non-valve containing prosthetics and repairs were associated with a HR of 3.34 at 0–6 months but no increase risk >6 months. The current European endocarditis prophylaxis guidelines (referred to elsewhere in this chapter) and US guidelines, accordingly recommend antibiotic prophylaxis for 6 months after complete closure of a defect with prosthetic material, regardless of

patient-years [60].

28 Advanced Concepts in Endocarditis

**7.6. Pulmonary valve and tetralogy of Fallot**

**7.7. Post-surgical and catheter intervention**

risk of approximately 1–2.3 per 1000 patient-years [12, 58].

higher for a palliative shunt, at 8.2 per 1000 patient-years [60].

whether it be percutaneously or surgically treated [57, 61].

data was insufficient in the operated group to calculate the ratio [50].

Hypertrophic cardiomyopathy (HCM) is an inherited genetic disorder characterised by myocardial thickening. Often this is asymmetric with marked involvement of the ventricular septum. In this setting, increased gradients are generated through the left ventricular outflow tract (LVOT) and if sufficient, result in systolic motion of the anterior mitral leaflet (SAM). Repeated trauma from contact between endocardial surfaces, results in formation of plaques on the ventricular septum, at the point of contact with the MV leaflet. There are altered mechanical and haemodynamic forces acting on the MV, AV and LVOT. This predisposes to endothelial trauma and inflammation, with the potential formation of NBTE and IE at multiple sites [17].

## **8.2. Echocardiographic diagnosis and predictors of endocarditis risk**

Modern echocardiography is readily utilised to diagnose hypertrophic obstructive cardiomyopathy (HOCM). Typical criteria include an unexplained septal thickness of ≥15 mm and LVOT obstruction as a resting or provoked gradient of ≥30 mmHg. In one study [66], the incidence of IE was 1.4 per 1000 patient-years. Echocardiographic predictors of IE risk included: (i) resting LVOT obstruction with incidence of 3.0 per 1000 patient-years, and (ii) marked left atrial dilatation (in presence of resting LVOT obstruction) with incidence of 9.2 per 1000 patientyears. Left ventricular wall thickness was not associated with increased risk [66].

There is overall conflicting data, with some studies finding IE is related to LVOT gradient and a propensity for MV infection, whilst other studies have found the contrary, with no particular relation to LVOT gradient or predilection for AV or MV [67].
