Background Primary percutaneous coronary intervention (PCI) is a treatment of choice for patients with STsegment elevation myocardial infarction (STEMI). Of the various risk stratification scores that have been introduced, the thrombolysis in myocardial infarction (TIMI) score is among the most used modalities. Patients with a TIMI score of five or higher are classified as high-risk patients with higher rates of adverse events. Therefore, this study aimed to determine the rate of adverse events after primary PCI in patients presenting with STEMI and a TIMI score of five or higher. Methodology This descriptive study was conducted at the cardiology department of the Liaquat National Hospital, Karachi, from February 2018 to August 2018. The patients included in this study consisted of a total of 150 men and women who presented to the ED with concerns of chest pain and were diagnosed with STEMI and had a TIMI score of five or higher. Consultant cardiologists performed primary PCI procedures, and any post-procedure adverse events were recorded during the patients' hospital stays (up to one week), including mortality, heart failure, cardiogenic shock, and ventricular arrhythmias. Results The study population was 83.3% male and 16.7% female patients, and the mean age was 54.0 ± 9.4 years. The mean BMI was 27.34 ± 2.76 kg/m 2. The mean TIMI score was 9.19 ± 2.71, with a TIMI score higher than eight for 52.7% of patients. Death was observed in 18.7% of cases, heart failure in 21.3% of cases, cardiogenic shock in 13.3% of cases, and ventricular arrhythmia in 22.0% of cases. Conclusion A TIMI risk score of five or higher can identify patients at high risk not only for mortality, but also for heart failure, cardiogenic shock, and ventricular arrhythmias.