The research aimed to study the effect of dexmedetomidine combined with bundle strategy on the cardiac function of patients with severe sepsis through pyramid speckle tracking algorithm-based echocardiography, expected to provide reference for its clinical treatment. 98 patients with severe sepsis or septic shock admitted to the hospital were selected as the research subjects, and they were equally divided into experimental group (dexmedetomidine + bundle strategy) and control group (dexmedetomidine + routine nursing), with 49 in each. Ultrasonic cardiogram examination was performed on patients before and after treatment, and the pyramid-based speckle tracking (PST) algorithm was designed and used. The results showed that the running time of the PST algorithm (105.25 s) was less than that of the BM algorithm (336.41 s), and the difference was statistically significant ( P < 0.05 ), and the systolic blood pressure, diastolic blood pressure, left ventricular wall, and heart rate of the experimental group before treatment were not significantly different from those of the control group ( P > 0.05 ). The ultrasound index results found that the ejection fraction (EF) and fractional shortening (FS) of the two groups of patients showed a downward trend over time (1–7 days), while the E/A ratio showed an upward trend, and the E/A ratio of the experimental group was significantly greater than the control group ( P < 0.05 ). The systolic blood pressure, diastolic blood pressure, left ventricular wall, and heart rate of the two groups of patients showed a downward trend over time (1–7 days), and the systolic blood pressure, diastolic blood pressure, left ventricular wall, and heart rate of the experimental group were significantly lower than those of the control group ( P < 0.05 ). The 28-day mechanical ventilation time (6.97 ± 3.11 days), intensive care unit (ICU) stay time (9.18 ± 2.86 days), and the 28-day mortality rate (15.31%) of the experimental group were lower than those of the control group (6.97 ± 3.11 days; 13.08 ± 2.53 days; 31.95%) ( P < 0.05 ). In conclusion, the PST algorithm can effectively improve the quality of echocardiography and assist physicians in clinical evaluation, and dexmedetomidine combined with bundle strategy can stabilize the heart rate and reduce myocardial oxygen consumption in severe sepsis, while effectively shortens the recovery time and improves the overall prognosis.