A 58-year-old man with chronic hypertension (BP 160/95 mmHg) presents with exertional chest pain. Echocardiography shows concentric left ventricular hypertrophy. During cardiac catheterization, the phase marked **A** in the Wiggers diagram is noted to have markedly elevated wall tension. According to the LaPlace law, which of the following best explains the pathophysiology of myocardial ischemia during this phase in this patient?