# Clinical Cases: Cardiovascular Pharmacology

## Case 1: Drug-Induced QT Prolongation and Torsades de Pointes

### Clinical Scenario
A 72-year-old female presents to the emergency department after a syncopal episode while taking multiple medications, including a recently started antibiotic.

### Patient Demographics
- **Age:** 72 years
- **Sex:** Female
- **Weight:** 62 kg

### Chief Complaint
Syncope without warning while standing in the kitchen

### History of Present Illness
The patient has a history of atrial fibrillation (on amiodarone 200 mg daily for 5 years), hypertension, and type 2 diabetes. She was recently started on levofloxacin 750 mg daily for a urinary tract infection 3 days ago. Today, she experienced sudden loss of consciousness without prodrome, witnessed by her husband who described "shaking" lasting approximately 30 seconds. She has also been taking ondansetron for nausea.

### Medications
- Amiodarone 200 mg daily
- Levofloxacin 750 mg daily (started 3 days ago)
- Ondansetron 4 mg PRN (2-3 times daily)
- Metformin 1000 mg twice daily
- Lisinopril 10 mg daily

### Physical Examination
- **Vital Signs:** BP 128/78 mmHg, HR 82 bpm (irregular), RR 16, T 37.0C
- **General:** Alert, oriented, slightly fatigued
- **Cardiovascular:** Irregular rhythm, no murmurs
- **Neurological:** No focal deficits, no post-ictal state

### Workup and Results
| Test | Result | Reference Range |
|------|--------|-----------------|
| Potassium | 3.1 mEq/L | 3.5-5.0 mEq/L |
| Magnesium | 1.4 mEq/L | 1.5-2.5 mEq/L |
| Calcium | 9.0 mg/dL | 8.5-10.5 mg/dL |
| TSH | 2.8 mIU/L | 0.4-4.0 mIU/L |
| Creatinine | 1.3 mg/dL | 0.6-1.2 mg/dL |

**ECG on arrival:** Atrial fibrillation, QTc 580 ms (prolonged)

**Telemetry recording during syncopal episode:** Torsades de pointes degenerating to ventricular fibrillation with spontaneous conversion

### Diagnosis
**Drug-induced QT prolongation with Torsades de Pointes** from multiple QT-prolonging drugs (amiodarone, levofloxacin, ondansetron) and electrolyte abnormalities

### Cardiovascular Pharmacology Principles Illustrated
1. **QT prolongation mechanism:** Multiple drugs block the hERG (IKr) potassium channel, delaying ventricular repolarization.
2. **Additive risk:** Combining multiple QT-prolonging drugs dramatically increases risk of torsades.
3. **Risk factors:** Hypokalemia and hypomagnesemia lower the threshold for torsades.
4. **Drug classes implicated:** Fluoroquinolones, Class III antiarrhythmics (amiodarone), antiemetics (ondansetron), many antipsychotics.
5. **Female sex:** Women have inherently longer QTc and higher torsades risk.

### Treatment
1. **Immediate:** IV magnesium sulfate 2 g over 10 minutes (first-line for torsades)
2. **Discontinue all QT-prolonging agents:** Stop levofloxacin, ondansetron
3. **Electrolyte repletion:** IV potassium to K+ >4.0 mEq/L, magnesium to Mg2+ >2.0 mEq/L
4. **Overdrive pacing or isoproterenol:** If recurrent torsades (increases heart rate, shortens QT)
5. **Alternative antibiotic:** Nitrofurantoin or amoxicillin-clavulanate for UTI
6. **Review all medications** for QT-prolonging potential
7. **Cardiology consultation** for amiodarone risk-benefit discussion

### Clinical Image

![Torsades de Pointes](case_01_image.jpg)

*Torsades de pointes ("twisting of the points") - a polymorphic ventricular tachycardia characterized by QRS complexes that twist around the baseline. This arrhythmia occurs in the setting of prolonged QT interval and can degenerate to ventricular fibrillation.*

**Image Source:** Wikimedia Commons
**License:** Public Domain
**URL:** https://commons.wikimedia.org/wiki/File:Torsades_de_pointes.svg

---

## Case 2: ACE Inhibitor-Induced Angioedema

### Clinical Scenario
A 58-year-old African American male presents with acute swelling of his lips and tongue 6 months after starting lisinopril.

### Patient Demographics
- **Age:** 58 years
- **Sex:** Male
- **Ethnicity:** African American
- **Weight:** 95 kg

### Chief Complaint
Progressive lip and tongue swelling for 3 hours

### History of Present Illness
The patient started lisinopril 10 mg daily 6 months ago for hypertension. He has tolerated the medication well without cough. This morning, he woke up with mild lip swelling that has progressively worsened over 3 hours. He now has difficulty speaking due to tongue swelling and is beginning to feel "tightness" in his throat.

### Physical Examination
- **Vital Signs:** BP 142/88 mmHg, HR 92 bpm, RR 20, T 37.0C, SpO2 97% on RA
- **General:** Anxious, muffled voice, drooling
- **HEENT:**
  - Marked edema of upper and lower lips
  - Tongue swelling extending to base
  - Uvula edema visible
  - No urticaria or rash
- **Respiratory:** Inspiratory stridor, no wheezing
- **Cardiovascular:** Tachycardic, regular
- **Skin:** No hives, no erythema

### Workup and Results
| Test | Result | Reference Range |
|------|--------|-----------------|
| C4 complement | 22 mg/dL | 15-45 mg/dL |
| Tryptase | 5 ng/mL | <11 ng/mL |
| IgE | 45 IU/mL | <100 IU/mL |
| CBC | Normal | - |

**Laryngoscopy:** Significant edema of base of tongue and supraglottic structures

### Diagnosis
**ACE inhibitor-induced angioedema** (bradykinin-mediated, not IgE-mediated)

### Cardiovascular Pharmacology Principles Illustrated
1. **Bradykinin mechanism:** ACE degrades bradykinin; ACE inhibition leads to bradykinin accumulation.
2. **Delayed onset:** Can occur years after starting ACE inhibitor (unlike allergic reactions).
3. **Not histamine-mediated:** Antihistamines and epinephrine are less effective; normal tryptase and IgE.
4. **Racial predisposition:** African Americans have 3-5x higher risk due to differences in bradykinin metabolism.
5. **ACE inhibitor cough:** Same mechanism (bradykinin accumulation in airways).

### Treatment
1. **Airway management:** Prepare for emergent airway; anesthesia and ENT backup
2. **Discontinue ACE inhibitor permanently**
3. **Epinephrine 0.3-0.5 mg IM:** May provide some benefit
4. **Fresh frozen plasma:** Contains ACE and kininase II to degrade bradykinin
5. **Icatibant (bradykinin B2 receptor antagonist):** If available, highly effective
6. **C1 esterase inhibitor concentrate:** May help in severe cases
7. **Observation:** Minimum 24-48 hours due to biphasic progression
8. **Alternative antihypertensive:** ARBs are usually safe but carry small cross-reactivity risk

### Clinical Image

![Wide Complex Tachycardia](case_02_image.jpg)

*ECG tracing demonstrating wide QRS complex tachycardia pattern. While this image shows a different arrhythmia, it demonstrates ECG changes that can occur with cardiovascular drug toxicity and interactions.*

**Image Source:** Wikimedia Commons
**License:** Public Domain
**URL:** https://commons.wikimedia.org/wiki/File:Wide_complex_tachycardia.svg

---

## Case 3: Heparin-Induced Thrombocytopenia (HIT)

### Clinical Scenario
A 67-year-old male develops new thrombosis and falling platelet count 8 days after starting heparin for a pulmonary embolism.

### Patient Demographics
- **Age:** 67 years
- **Sex:** Male
- **Weight:** 85 kg

### Chief Complaint
Painful, swollen left arm with darkened skin

### History of Present Illness
The patient was admitted 10 days ago with pulmonary embolism and started on unfractionated heparin infusion, later transitioned to warfarin. His INR is now therapeutic at 2.5. Over the past 2 days, he developed progressive pain and swelling in his left arm with bluish discoloration. His platelet count has dropped from 245,000 to 68,000 over the past 4 days.

### Physical Examination
- **Vital Signs:** BP 135/82 mmHg, HR 88 bpm, RR 18, T 37.8C
- **General:** Anxious, uncomfortable
- **Left upper extremity:**
  - Tense swelling from hand to upper arm
  - Bluish-purple discoloration of fingers
  - Diminished radial pulse
  - Tender to palpation
- **Skin:** Erythema and induration at heparin injection sites on abdomen

### Workup and Results
| Test | Result | Reference Range |
|------|--------|-----------------|
| Platelet count (Day 1) | 245,000/mcL | 150,000-400,000/mcL |
| Platelet count (Day 6) | 156,000/mcL | - |
| Platelet count (Day 10) | 68,000/mcL | - |
| 4Ts Score | 7 (high probability) | - |
| Anti-PF4/heparin antibody | Positive (OD 2.4) | <0.4 |
| Serotonin release assay | 95% release | <20% |
| INR | 2.5 | 2.0-3.0 |

**Doppler ultrasound:** Acute thrombosis of left axillary and subclavian veins

### Diagnosis
**Heparin-Induced Thrombocytopenia type II (HIT)** with limb-threatening venous thrombosis

### Cardiovascular Pharmacology Principles Illustrated
1. **Immune-mediated mechanism:** Antibodies form against complexes of heparin and platelet factor 4 (PF4).
2. **Paradoxical thrombosis:** Despite thrombocytopenia, HIT causes thrombosis (not bleeding) through platelet activation.
3. **Timing:** Typically occurs 5-10 days after heparin exposure (or earlier with prior exposure).
4. **All heparins implicated:** UFH > LMWH, but both can cause HIT.
5. **Warfarin contraindicated:** Can worsen thrombosis during acute HIT by depleting protein C.

### Treatment
1. **Stop ALL heparin immediately** (including flushes, coated catheters)
2. **Stop warfarin** (can cause venous limb gangrene in acute HIT)
3. **Vitamin K 10 mg PO** to reverse warfarin
4. **Start alternative anticoagulant:**
   - Argatroban (direct thrombin inhibitor) - preferred in hepatic impairment concerns
   - Bivalirudin
   - Fondaparinux (off-label but commonly used)
5. **Continue anticoagulation** until platelet recovery and therapeutic on long-term agent
6. **DO NOT transfuse platelets** (fuels thrombosis)
7. **Vascular surgery consultation** for limb-threatening ischemia
8. **Transition to DOAC** (not warfarin) for long-term anticoagulation

### Key Learning Points
- HIT is a hypercoagulable state despite low platelets
- 4Ts score helps estimate pretest probability
- Never use heparin (including LMWH) in patients with HIT history
- Argatroban monitoring uses aPTT; transitions to warfarin are complex
- Document HIT allergy prominently in medical record