A 58-year-old woman presents to the emergency department from an outpatient clinic with complaints of persistent lightheadedness and intermittent palpitations that started shortly after receiving prochlorperazine for severe, protracted gastroenteritis. She reports several days of significant vomiting and poor oral intake. Upon arrival, her blood pressure is 95/55 mm Hg, heart rate is 180 beats/min and irregular, and respiratory rate is 18 breaths/min. Oxygen saturation is 95% on room air. Physical examination reveals dry mucous membranes and diminished skin turgor. Cardiac auscultation reveals a rapid, irregularly irregular rhythm with variable S1 and S2 sounds. Neurological examination is unremarkable. An electrocardiogram is immediately obtained. Based on the presented clinical picture and electrocardiographic findings, what is the most likely cardiac rhythm and the immediate therapeutic intervention required?

A 32-year-old woman, admitted to a general medical ward for severe gastroenteritis with intractable vomiting, develops sudden onset of lightheadedness and palpitations. Her medical history is otherwise unremarkable. On assessment, her temperature is 36.8°C, pulse is 130/min, blood pressure is 90/50 mmHg, respirations are 18/min, and oxygen saturation is 98% on room air. She appears anxious but is oriented to person, place, and time. Peripheral pulses are rapid and thready. A review of her continuous cardiac monitoring shows a polymorphic wide-complex tachycardia with a characteristic waxing and waning amplitude, twisting around the isoelectric baseline. Identify the most likely cardiac arrhythmia and the immediate therapeutic intervention indicated for this patient.

A 62-year-old woman with a history of hypertension, type 2 diabetes mellitus, coronary artery disease requiring drug-eluting stent placement, and heart failure with reduced ejection fraction recently presented to her cardiologist's office with worsening exertional dyspnea and lower extremity edema after a viral illness. She was prescribed an increased dose of a loop diuretic. Three days later, while admitted to the hospital for further management of decompensated heart failure, she suddenly develops symptomatic palpitations and lightheadedness. Her telemetry monitoring reveals a polymorphic ventricular tachycardia with a characteristic "twisting" of the QRS complexes around the isoelectric line, as shown in Figure A. What is the most appropriate immediate therapeutic intervention and what long-term complication should be monitored in this patient?

A 62-year-old woman presents to the emergency department after experiencing a sudden episode of lightheadedness and near-syncope while reaching for something on a high shelf. She reports intermittent palpitations and a general sense of unease over the past few days. Her medical history includes well-controlled hypertension and dyslipidemia, and she recently started taking a medication for nausea. She adheres to her prescribed medications. Her temperature is 37.2°C, blood pressure is 98/60 mmHg, pulse is 75/min and irregular, respirations are 14/min, and oxygen saturation is 97% on room air. A physical exam reveals a patient who appears anxious but alert. Auscultation of the lungs reveals clear breath sounds bilaterally. Cardiac exam shows an S1 and S2 present with an irregularly irregular rhythm and thready peripheral pulses. No murmurs, rubs, or gallops are appreciated. Neurological exam is non-focal. An ECG is ordered as seen in Figure A. Based on the clinical presentation and diagnostic findings, what is the most likely cardiac rhythm disturbance and the immediate therapeutic intervention?

A 40-year-old woman presents to an outpatient clinic with a chief complaint of recurrent episodes of lightheadedness and palpitations over the past week. She reports a chronic history of heavy alcohol consumption, noting that her nutritional intake has been poor recently due to increasing alcohol use. She denies chest pain, shortness of breath, or focal neurological deficits. Her medical history is otherwise unremarkable, and she is not currently taking any prescribed medications. On physical examination, she appears fatigued, with dry oral mucous membranes and reduced skin turgor. Her vital signs are: temperature 37.0°C, pulse 92 beats/min, blood pressure 95/60 mmHg (with orthostatic drop to 85/50 mmHg upon standing), and respiratory rate 18 breaths/min. An electrocardiogram obtained during an episode reveals a polymorphic wide-complex tachycardia with a characteristic "twisting" of the QRS axis. Considering the patient's presentation and ECG findings, what is the most likely underlying diagnosis and the immediate management strategy?

A 6-year-old girl is brought to a specialized pediatric clinic by her parents, who are increasingly concerned about recurrent episodes of sudden loss of consciousness. Initially, these events were misattributed to seizure activity by her primary care physician, and she was started on valproic acid without significant improvement. Her parents describe that these episodes, which they call 'fainting spells,' often occur when she is startled by loud noises, like a sudden clap or a dropped object, or during moments of excitement while playing. They also report that she frequently misses verbal cues, requiring them to repeat themselves or speak loudly, and that her teachers at school have raised concerns about her hearing. A paternal cousin died unexpectedly in early childhood from an unknown cardiac cause.On examination, her vital signs are stable: temperature 37.1°C, blood pressure 100/50 mmHg, heart rate 95 beats/min, respiratory rate 22 breaths/min. A general physical examination is unremarkable except for a noted diminished response to auditory stimuli. A routine electroencephalogram (EEG) conducted previously was non-diagnostic, showing no epileptiform activity. Electrocardiograms were performed: the first (Figure A) revealed a prolonged corrected QT interval, and the second (Figure B), taken during an acute episode triggered by a sudden loud noise, showed a polymorphic ventricular tachycardia with a characteristic twisting appearance.Laboratory results from a recent admission for one of these episodes are as follows:Considering this clinical presentation and findings, what is the most likely underlying diagnosis and the immediate management strategy?

A 42-year-old woman with a history of bipolar disorder and recent admission to a general medical ward for dehydration is reviewed by the medical team. She was recently started on quetiapine for mood stabilization. On her third hospital day, she reports intermittent episodes of dizziness and a sensation of her heart "skipping beats." Her physical examination reveals a blood pressure of 118/72 mmHg and a regular pulse of 88 beats/min initially, but during an episode, her pulse increases to 140-150 bpm, and she appears pale. An urgent electrocardiogram (ECG) is performed. The ECG shows a prolonged QTc interval of 520 ms during sinus rhythm, with subsequent episodes of polymorphic ventricular tachycardia characterized by QRS complexes twisting around an imaginary baseline. Her serum potassium level is 3.7 mmol/L and serum magnesium level is 0.7 mmol/L. What is the most likely diagnosis and the immediate therapeutic intervention required to stabilize this patient and prevent further life-threatening arrhythmias?

A 28-year-old female presents to the emergency department after experiencing a sudden syncopal episode while at rest. Her partner reports that she has had similar brief, unexplained 'fainting spells' since childhood, which were previously attributed to vasovagal causes, but no definitive diagnosis was made. She also has a documented history of severe bilateral sensorineural hearing loss diagnosed in early childhood, for which she uses hearing aids. There is a family history of a paternal aunt who died suddenly and unexpectedly in her early thirties. On examination, her vital signs are stable: temperature 37.0°C, blood pressure 118/76 mmHg, pulse 78/min, respirations 16/min, and oxygen saturation 99% on room air. Cardiac auscultation reveals a regular rhythm with no murmurs, rubs, or gallops. Neurological examination confirms sensorineural deafness but is otherwise unremarkable. A 12-lead electrocardiogram (ECG) is performed, showing sinus rhythm with marked QT interval prolongation (corrected QT interval >500 ms). Given her presentation and the most likely underlying condition, what is the immediate management strategy and the most appropriate long-term preventative measure for this patient?