Three-Dimensional Late Gadolinium Enhancement Cardiovascular Magnetic Resonance Predicts Inducibility of Ventricular Tachycardia in Adults With Repaired Tetralogy of Fallot.

BACKGROUND: Adults with repaired tetralogy of Fallot die prematurely from ventricular tachycardia (VT) and sudden cardiac death. Inducible VT predicts mortality. Ventricular scar, the key substrate for VT, can be noninvasively defined with late gadolinium enhancement (LGE) cardiovascular magnetic resonance but whether this relates to inducible VT is unknown. METHODS: Sixty-nine consecutive repaired tetralogy of Fallot patients (43 male, mean 40±15 years) clinically scheduled for invasive programmed VT-stimulation were prospectively recruited for prior 3-dimensional LGE cardiovascular magnetic resonance. Ventricular LGE was segmented and merged with reconstructed cardiac chambers and LGE volume measured. RESULTS: VT was induced in 22 (31%) patients. Univariable predictors of inducible VT included increased RV LGE (odds ratio [OR], 1.15; P=0.001 per cm3), increased nonapical vent LV LGE (OR, 1.09; P=0.008 per cm3), older age (OR, 1.6; P=0.01 per decile), QRS duration ≥180 ms (OR, 3.5; P=0.02), history of nonsustained VT (OR, 3.5; P=0.02), and previous clinical sustained VT (OR, 12.8; P=0.003); only prior sustained VT (OR, 8.02; P=0.02) remained independent in bivariable analyses after controlling for RV LGE volume (OR, 1.14; P=0.003). An RV LGE volume of 25 cm3 had 72% sensitivity and 81% specificity for predicting inducible VT (area under the curve, 0.81; P<0.001). At the extreme cutoffs for ruling-out and ruling-in inducible VT, RV LGE >10 cm3 was 100% sensitive and >36 cm3 was 100% specific for predicting inducible VT. CONCLUSIONS: Three-dimensional LGE cardiovascular magnetic resonance-defined scar burden is independently associated with inducible VT and may help refine patient selection for programmed VT-stimulation when applied to an at least intermediate clinical risk cohort.

Angiotensin II inhibition reduces stress sensitivity of hypothalamo-pituitary-adrenal axis in spontaneously hypertensive rats.

Angiotensin II type 1 (AT(1)) receptors are expressed within organs of the hypothalamo-pituitary-adrenal (HPA) axis and seem to be important for its stress responsiveness. Secretion of CRH, ACTH, and corticosterone (CORT) is increased by stimulation of AT(1) receptors. In the present study, we tested whether a blockade of the angiotensin II system attenuates the HPA axis reactivity in spontaneously hypertensive rats. Spontaneously hypertensive rats were treated with candesartan (2 mg/kg), ramipril (1 mg/kg), or mibefradil (12 mg/kg) for 5 wk. In addition to baseline levels, CORT and ACTH responses to injection of CRH (100 microg/kg) were monitored over 4 h. mRNA of CRH, proopiomelanocortin, AT(1A), AT(1B), and AT(2) receptors was quantified by real-time PCR. All treatments induced equivalent reductions of blood pressure and had no effect on baseline levels of CORT and ACTH. However, both candesartan and ramipril significantly reduced CRH-stimulated plasma levels of ACTH (-26 and -15%) and CORT (-36 and -18%) and lowered hypothalamic CRH mRNA (-25 and -29%). Mibefradil did not affect any of these parameters. Gene expression of AT(1A), AT(1B), and AT(2) receptors within the HPA axis was not altered by any drug. We show for the first time that antihypertensive treatment by inhibition of AT(1) receptors or angiotensin-converting enzyme attenuates HPA axis reactivity independently of blood pressure reduction. This action is solely evident after CRH stimulation but not under baseline conditions. Both a reduced pituitary sensitivity to CRH and a down-regulation of hypothalamic CRH expression have the potential to reduce HPA axis activity during chronic AT(1) blockade or angiotensin-converting enzyme inhibition.