Introduction: Aging, cardiovascular disease (CVD), and heart failure (HF) increase the coexisting morbidity (CM) burden. This study compared the contribution of HF with this increase in elderly patients hospitalized for CVD by comparing patients with and without HF. Methods: Consecutive patients aged >65 years, hospitalized with CVD, were included (104 with and 100 without HF). The prevalence of 10 common CM (hypertension, coronary artery disease, atrial fibrillation, diabetes, dyslipidemia, anemia, chronic kidney disease, chronic obstructive pulmonary disease, sleep apnea, and cancer) was examined. The CM burden was assessed with the CM index (number of CM/ patient) and multimorbidity (>= 2 CM/patient). Results: The CM index was significantly higher [5 (3-6) vs. 3 (2-4), p < 0.0001], whereas multimorbidity [94.2% vs. 86%, p = 0.06] marginally higher in CVD patients with HF than those without HF. Ordinal regression with test of proportional lines revealed that in CVD patients with HF, the odds for a high CM index were approximately 8 times higher compared with CVD patients without HF, given that age and LVEF were held constant. Conclusion: HF development was associated with a dramatic increase in the CM index in elderly patients with CVD who already have a high prevalence of multimorbidity. (C) 2022 Hellenic Society of Cardiology. Publishing services by Elsevier B.V.