Objective To investigate the therapeutic effects of the newly developed phosphodiesterase 5 inhibitor, CPD1, on pathological myocardial hypertrophy induced by abdominal aortic constriction (AAC) in rats, and its impact on activation of the autophagy signaling pathway in myocardial tissue. Methods Male Sprague Dawley rats weighing 180~200 g were divided randomly into five groups: Control, Sham, model (AAC), CPD1 treatment (AAC-CPD1,5 mg/kg), and sildenafil treatment (AAC-Sif, 20 mg/kg) groups. Rats in all groups except the Control group underwent blunt dissection of the abdominal aorta at the branch point of the left renal artery. Rats in the AAC and treatment groups also underwent constriction and ligation surgery, while rats in the Sham group underwent dissection without ligation. After 3 days of modeling, rats in the treatment groups received either CPD1 or sildenafil via gavage, while rats in the Control, Sham, and AAC groups received an equal volume of physiological saline by gavage, once daily for 8 weeks. Small-animal ultra-high-resolution echocardiography and left ventricular catheterization were employed to assess left heart function and the heart mass index, and expression levels of the hypertrophy indicator, atrial natriuretic peptide (ANP), the key autophagy pathway factor, p62, and LC3A/B in rat left heart tissue were evaluated by Western blot and reverse transcription-polymerase chain reaction. Results Abdominal aortic stenosis affected left heart function in rats, characterized by an increased cardiac mass index and significant enlargement of myocardial cell cross-sectional area. ANP expression levels in left heart tissue were significantly elevated (P<0.05), while autophagy signaling activity was reduced, with notable accumulation of LC3I protein and reduced conversion to LC3II. Expression levels of p62 protein were significantly increased. CPD1 and sildenafil significantly improved left ventricular function in AAC rats, reduced cardiac hypertrophy, inhibited expression levels of ANP and p62 proteins (P<0.05), activated autophagy signaling, and promoted the conversion of LC3I to LC3II. Notably, low-dose CPD1 treatment was equivalent to high-dose sildenafil. Conclusions CPD1 promotes the activation of the autophagy signaling pathway in left heart tissue, inhibits the expression of p62 and ANP, reduces the cross-sectional area of myocardial cells, and improves pathological myocardial hypertrophy and left heart function impairment caused by AAC. CPD1 also has the advantage of a lower effective dose compared with sildenafil, offering a new treatment option for pathological myocardial hypertrophy.