A 20-year-old woman had Goodpasture syndrome which progressed to chronic renal failure. She is 165 cm tall and weighs 55 kg. She now has blood pressure measurements in the range of 150/90 to 180/110 mm Hg, but does not regularly take medications. Laboratory studies show her blood urea nitrogen is over 100 mg/dL and she requires chronic dialysis. A chest x-ray shows an enlarged heart. The size of her heart is most likely to be the result of which of the following processes involving the myocardial fibers?