Scorpion stings are a public health issue in tropical and subtropical regions where these arachnids are endemic. Globally, an estimated 1.2 million scorpion stings occur annually, resulting in over 3,250 deaths.¹ In Mexico, the numbers are exceptionally high, specifically in Jalisco, Guerrero, Guanajuato, Michoacán, and Morelos, with 194,482 cases reported in 2023 and 287,581 cases recorded up to week 46 of 2024.^1-3

Scorpion venom contains a complex mixture of neurotoxins, cardiotoxins, and other bioactive compounds that can cause local and systemic clinical manifestations.⁴ Systemic toxicity includes neuromuscular symptoms such as paresthesia and muscle spasms, as well as cardiovascular manifestations like hypertension, tachycardia, and, in severe cases, myocardial dysfunction and shock.^5,6

Left-bundle branch block (LBBB) associated with scorpion envenomation is a rare and underdocumented cardiovascular manifestation. It reflects a disruption in the heart’s electrical conduction system, which may suggest myocardial ischemia or other underlying cardiac conditions.^7,8 However, the absence of elevated cardiac enzymes, such as troponin, raises questions about the underlying pathophysiological mechanisms involved.

Recent studies indicate that venom neurotoxins can alter autonomic homeostasis, inducing transient dysfunctions in the cardiovascular system without detectable myocardial damage.⁹ Furthermore, factors such as post-traumatic anxiety and somatosensory amplification could contribute to the persistent perception of symptoms such as precordial pain.^10,11

This is the case of a 58-year-old female patient who experienced precordial pain following a scorpion sting.

Medical History

The patient had no chronic degenerative diseases, no history of substance abuse, and no exposure to biomass. She reported an allergy to penicillin and a surgical history of two cesarean sections, and an oophorectomy.

Current Condition

The patient described the onset of precordial pain with an intensity of 6/10, exacerbated by movement. This condition began after a scorpion sting on July 30^th, 2023, on the third finger of her left hand. She mentioned discovering the presence of the scorpion in her clothing. She attributed the pain to the sting, which had persisted constantly since then. Initially treated at a Red Cross Unit, her condition was classified as Grade I scorpion envenomation (pain and paresthesia). During her stay, the clinical condition progressed to Grade III envenomation (precordial pain) within 30 minutes of medical attention. Management with parenteral solutions was initiated: 0.9% saline solution at 70 ml/hour, polyvalent anti-scorpion antivenom (4 doses), and dual analgesia (paracetamol 1 gram IV [intravenous] single dose + ketorolac 30 mg IV single dose).

Electrocardiographic findings later showed a new-onset LBBB. Supplemental oxygen was administered to achieve SpO2 > 94%, cardiac monitoring was initiated, and her transfer to her primary care facility was arranged. The patient reported that the pain radiated from the sting site to her shoulder and left thoracic area, with an initial intensity of 2/10, increasing to 5/10. Currently, she denies angina-equivalent symptoms and has no signs of vasovagal episodes. She was referred to a secondary-level care unit for evaluation and follow-up of precordial pain, where she was admitted on July 30^th, 2023, at 13:08.

Admission

The patient was admitted with vital signs of heart rate (HR) 71 beats per minute (bpm), respiratory rate (RR) 18 breaths/min, blood pressure (BP) 110/70 millimeters of mercury (mmHg), temperature of 36.3°C, and oxygen saturation (SpO2) of 99%. She was awake, alert, and oriented to time, place, person, and situation. Pupils were isochoric and normoreactive with a diameter of 2 mm. Facial symmetry was preserved, and speech was normal.

The cardiorespiratory examination showed well-ventilated lung fields without crackles or wheezes. The precordium was rhythmic, without additional sounds, and tender to palpation between the third and fifth intercostal spaces. The abdomen was distended due to adipose tissue, with normal peristalsis frequency and tone. It was soft and depressible, with no organomegaly or peritoneal irritation. The extremities were intact, without edema, and with normal muscle tone and strength.

The patient, in her sixth decade of life, was admitted to our ward for follow-up and management of precordial pain. Laboratory tests showed the same electrocardiographic (ECG) pattern as the EKG taken at the Red Cross. Cardiac biomarkers were requested, but the trace did not meet Sgarbossa criteria. However, continuous hemodynamic monitoring and telemetry were maintained. Due to the absence of a typical pain pattern suggestive of cardiac characteristics, aspirin (ASA) and analgesia were prescribed, with a dose of 150 milligrams (mg) taken orally (PO).

During her hospitalization, the patient did not exhibit signs of low-cardiac output; however, localized pain in the left upper extremity persisted. Two enzymatic determinations were negative, and she was discharged on August 1^st, 2023, at 07:14, with warning signs provided. She was advised to follow up with her family physician at her primary care unit. She was prescribed atorvastatin 20 mg every 24 hours, metoclopramide 10 mg every 8 hours if needed for nausea or vomiting, paracetamol 1 gram every 8 hours for 3 days, and an open emergency room appointment.

Laboratory Results

• July 30^th, 2023, 14:32 hours. Leukocytes (Leu) 5.9 x 10⁹/L, hemoglobin (Hb) 13.1 grams per deciliter (g/dL), hematocrit (Hct) 39.4%, platelets (Plt) 224 x 10⁹/L, lymphocytes (Lymph) 23%, neutrophils (Neut) 69.8%, prothrombin time (PT) 11.5 seconds, international normalized ratio (INR) 1, activated partial thromboplastin time (aPTT) 34.4 seconds, D-dimer 326 nanograms per milliliter (ng/mL), creatinine 0.7 milligrams per deciliter (mg/dL), glucose 90 mg/dL, blood urea nitrogen (BUN) 18 mg/dL, urea 38 mg/dL, gamma-glutamyl transferase (GGT) 39 units per liter (U/L), total bilirubin (TB) 1.1 mg/dL, indirect bilirubin (IB) 1.2 mg/dL, direct bilirubin (DB) 0 mg/dL, albumin (Alb) 3.7 g/dL, alanine aminotransferase (ALT) 22 U/L, aspartate aminotransferase (AST) 27 U/L, alkaline phosphatase (ALP) 65 U/L, phosphorus 3.9 mg/dL, calcium 9 mg/dL, chloride 109 milliequivalents per liter (mEq/L), potassium 4 mEq/L, sodium 139 mEq/L, magnesium 1.8 mg/dL, creatine phosphokinase (CPK) 132 U/L, CPK-MB 14 U/L, lactate dehydrogenase (LDH) 190 U/L, troponin 0.012 nanograms per milliliter (ng/mL).
• Enzymatic control. July 30th, 2023, 21: 37 hrs: CPK 133 U/L, CPK - MB 15 U/L, troponin 0.012 ng/mL.

Additional Tests

• Electrocardiogram (ECG). 12-lead, recorded at 25 millimeters per second (mm/s) 10 millimeters per millivolt (mm/mV), sinus rhythm at 75 bpm, P wave duration of 0.08 seconds positive in all leads except aVR, QRS duration 0.18 s with left-bundle branch block pattern (Figure 1).