Myocardial remodeling in chronic heart disease also involves the giant protein titin, thereby affecting passive stiffness. End-stage failing human hearts (CAD and DCM patients) or terminally failing rat hearts following myocardial infarction express increased proportions of long titin isoforms (N2BA type, 3.2-3.4 MDa) and have reduced passive stiffness at the myofibril level. Here we wanted to know whether titin-isoform switching is triggered by chronic afterload increase. We generated the renal artery clip 2K1C rat model, which develops hypertension causing LV pressure overload and hypertrophy. Both 6 weeks and 8 months following clipping, rats exhibited a ~40% increase in mean blood pressure, a ~50% increase in LV-weight:body-weight ratio, and concentric cardiac hypertrophy with low fibrosis (estimated by collagen staining), compared to Sham-operated hearts. Echocardiography and hemodynamics of 8-month-clipped hearts confirmed the hypertrophy and showed a prolonged relaxation constant, Tau, but preserved EF, dp/dt, fractional shortening, and EDP. Real-time RT-PCR to quantify the expression of titin mRNA transcripts demonstrated a small shift toward the short, stiff N2B variant (3.0 MDa) in hypertrophic hearts. However, at neither time point did the 2K1C hearts reveal changes in their titin protein-expression pattern. Thus, chronic afterload increase may not be the trigger for titin-isoform shifting. Possibly, modifications in titin expression and sarcomeric passive stiffness in failing hearts follow from chronic increase in preload.