He is short of breath, with cool, clammy skin. After treatment his wedge pressure is 15 mmHg. He presents to the ER with two hours of midchest and upper abdominal pain the day before, with faintness and nausea. The weakness has continued. There is no neck vein distension.
Lungs are clear.
Heart sounds are distant, without a murmur. A soft S4 is heard but no S3. There is no edema. A Swan-Ganz catheter is placed. Explain the pathophysiology, based on these data.