A 25-year-old healthy volunteer participates in a cardiac physiology experiment and receives an intravenous infusion of a beta-1 agonist. Vital signs show HR 98 bpm, BP 128/76 mmHg, RR 16, temp 37°C, SpO2 98% on room air. ECG demonstrates increased slope of phase 4 depolarization in sinoatrial node pacemaker cells. The volunteer denies chest pain or dyspnea. Which of the following changes is the most direct result of enhanced automaticity?
- A)Prolonged QT interval due to delayed repolarization
- B)Faster heart rate from enhanced SA node automaticityGABARITO
- C)Loss of the ventricular plateau phase
- D)Complete AV block due to suppressed conduction
- E)Slower heart rate from reduced automaticity
Explicação
Faster heart rate from enhanced SA node automaticity is correct. Sympathetic stimulation increases the slope of phase 4 depolarization in nodal tissue by enhancing funny current and calcium currents, allowing threshold to be reached sooner. This increases hear... Ver explicação completa e trilha adaptativa →