Download files
Abstract
Cardiomyopathies are heterogeneous disorders that result in significant morbidity and mortality.
This thesis evaluated subclinical left ventricular (LV) dysfunction in cardiomyopathy subtypes, namely radiation induced heart disease (RIHD), cardiac amyloidosis (CA) and Anderson-Fabry disease (AFD). The unifying theme of 2 dimensional (2D) LV strain imaging assessment was explored.
We hypothesized that LV strain and strain rate (SR) are more sensitive markers of subclinical changes in LV global and regional function than conventional methods.
RIHD was evaluated using 2D strain in a longitudinal study of left sided breast cancer patients undergoing radiotherapy; at baseline, during treatment and at 6 weeks post treatment. Reduced global longitudinal strain (GLS) was detected during radiotherapy and at 6 weeks post treatment despite preserved LVEF. A modest correlation of global strain reduction to mean heart dose was observed. Differential planar strain alterations with reduced longitudinal and radial strain and preserved circumferential strain was observed. The largest decrement of strain occurred in the LV apical segments, corresponding to segments receiving the highest radiation dose.
Cardiomyopathy with increased LV wall thickness including cardiac amyloidosis (CA), hypertension and AFD were studied and compared to age and gender matched normal controls. Differential planar strain reduction occurs in CA
compared to hypertension and normal controls. GLS and radial strain were reduced with preservation of circumferential strain until severe diastolic dysfunction develops. Regional heterogeneity was observed with basal and mid segmental strain reduction and relative sparing of apical strain. Longitudinal systolic SR was an independent predictor of mortality and restrictive filling pattern in CA.
2D strain detected subclinical LV dysfunction in patients with AFD patients despite preserved LVEF. Gender related differential strain reduction was observed; though diminished when compared to controls, greater reduction was seen in hemizygous males. In heterozygous females, reduced GLS was observed despite normal left ventricular wall thickness. Strain parameters were significantly decreased in patients with increased wall thickness.
Our findings underscored that application of 2D strain imaging is a sensitive tool in the detection of subclinical cardiac dysfunction in asymptomatic patients. This has implications on risk stratification, preventative measures and early initiation of targeted cardio-protective treatment.