A 65-year-old man presents for a routine physical examination. He is asymptomatic and denies dyspnea, orthopnea, or palpitations. Vital signs: heart rate 78/min, blood pressure 142/88 mm Hg, respiratory rate 16/min, oxygen saturation 98% on room air. On cardiac auscultation, a holosystolic murmur is heard best at the left lower sternal border (4th-5th intercostal space). The murmur increases in intensity during inspiration and decreases during expiration. Which of the following physiologic mechanisms best explains the increase in murmur intensity during inspiration?
- A)Decreased intrathoracic pressure increases venous return to the right heartGABARITO
- B)Increased pulmonary vascular capacitance reduces right ventricular afterload
- C)Negative intrathoracic pressure decreases left ventricular preload
- D)Increased sympathetic tone enhances right ventricular contractility
- E)Positive airway pressure reduces systemic vascular resistance
Explicação
During inspiration, intrathoracic pressure becomes more negative, which increases venous return to the right heart. This increases right ventricular stroke volume, resulting in increased flow across a tricuspid regurgitation jet (tricuspid insufficiency murmur... Ver explicação completa e trilha adaptativa →