During isovolumeric contraction in the cardiac cycle, which of the following events accurately describes the pressure–volume relationship of the left ventricle?

• A Left ventricular pressure rises steeply while volume remains constant and both AV and aortic valves are closed ✓
• B Left ventricular volume decreases while pressure increases and the mitral valve is open
• C Aortic valve opens as left ventricular pressure exceeds pulmonary artery pressure
• D Left ventricular pressure equals aortic pressure throughout this phase

Explanation

Isovolumeric contraction begins with closure of the mitral valve (marking the onset of systole) and ends when LV pressure exceeds aortic diastolic pressure, opening the aortic valve. During this interval both AV and aortic valves are closed, so ventricular volume is constant (isovolumic) while pressure rises rapidly. The aortic valve opens when LV pressure surpasses aortic pressure (~80 mmHg at rest), not pulmonary artery pressure.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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