Background: Spinal anesthesia in cardiac-compromised patients carries a high risk of hypotension and hemodynamic instability, which may exacerbate underlying cardiovascular conditions. Optimizing anesthetic technique is critical to ensure perioperative safety while providing effective analgesia. Aim of the study: To assess the efficacy and safety of isobaric bupivacaine for spinal anesthesia in cardiac-compromised patients undergoing lower limb surgery. Methods: In this prospective, comparative study, 60 patients with ASA II–III status and documented cardiac compromise were allocated into two groups (n=30 each): the Isobaric Bupivacaine group received 0.5% isobaric bupivacaine, while the control group received standard spinal anesthesia. Allocation was concealed using sealed opaque envelopes. Intraoperative hemodynamics, onset and duration of sensory and motor block, incidences of hypotension, bradycardia, and other adverse events were recorded. Postoperative pain was assessed using the Visual Analog Scale (VAS) at predefined intervals, and analgesic consumption, including opioid requirements and time to first analgesic request, was documented. Result: Baseline demographics, comorbidities, and ASA physical status were comparable between groups. The Isobaric Bupivacaine group demonstrated a faster onset of sensory (6.3 ± 1.1 vs. 7.8 ± 1.4 min, p<0.001) and motor block (8.1 ± 1.2 vs. 9.4 ± 1.3 min, p=0.002). Clinically significant hypotension occurred less frequently (10.0% vs. 30.0%, p=0.036), and vasopressor requirement was reduced (6.7% vs. 23.3%, p=0.041). Postoperative pain scores were consistently lower at all measured time points (VAS at 24 h: 2.3 ± 0.8 vs. 3.9 ± 1.0, p<0.001), total 24-hour opioid consumption was decreased (12.3 ± 3.1 mg vs. 21.0 ± 4.6 mg, p<0.001), fewer rescue doses were needed (median 1 vs. 3, p<0.001), and time to first analgesic request was prolonged (212 ± 26 vs. 181 ± 23 min, p<0.001). Other adverse events, including bradycardia, nausea