This man is deteriorating from cardiac tamponade, a condition in which blood is pooling around the heart and hindering its ability to fill during diastole (relaxation).

Doctors should suspect cardiac tamponade when a patient has hypotension, muffled heart sounds, and jugular venous distention (Beck's triad). Ultrasound will show a fluid collection in the pericardial sac surrounding the heart. Treatment is with immediate pericardiocentesis and fluid resuscitation.

Tension pneumothorax occurs when damage to the lung results in leakage of air into the pleural space. This causes equilibration of pressures between the lung and pleural space, leading to difficulty during inhalation. Positive pressure ventilation can help alleviate this condition. A splenic laceration will result in internal bleeding in the upper left quadrant of the abdomen. Pelvic fractures generally result from trauma during a fall or lateral impact and may cause damage to pelvic organs, but would not likely be linked to cardiac abnormalities. Acute myocardial infarction, or heart attack, occurs from blockage of or damage to the coronary arteries, resulting in a loss of blood flow to the tissues of the heart.

If the sinoatrial node becomes damaged and is unable to drive the rate of spontaneous depolarization in the heart (at its normal rate of 60-100 beats per minute), other cardiac pacemaker cells exist to ensure that the heart continues beating. The atrioventricular node is also known as the secondary pacemaker because these cells spontaneously discharge at a rate of 40-60 beats per minute. It is worth noting that if both the sinoatrial and atrioventricular nodes are damaged, the bundle branches, and Purkinje fibers are also capable of producing a spontaneous action potential at a rate of 30-40 beats per minute.

Aortic regurgitation is the term for leaky, insufficient valves. Aortic regurgitation can be repaired via a valve replacement procedure. Aortic stenosis is hardening of the arteries. Pulmonary embolisms is a blockage in one of the pulmonary arteries. Hypertension is also known as high blood pressure.

Troponin is a complex of proteins that play an important role in skeletal and cardiac muscle contraction. Troponin is released into the bloodstream when there is damage to the heart. This is a common diagnostic laboratory test for patients with heart problems or chest pain. 

Myocardial ischemia occurs when the heart demands more oxygen than the coronary arteries can supply. Ischemia means lack of blood. The ability for the coronary circulation to deliver oxygen may be reduced due to the formation of a blood clot, embolism, or atherosclerosis. Premature ventricular contraction and atrial fibrillation are irregular heart beats that can result in arrhythmias and, in some cases more serious complications. Coronary artery disease involves damage (usually via plaque deposition) to the arteries that supply the heart muscle. Congestive heart failure involves any one or more issues with the strength of the heart muscle.

The heart has four chambers divided into left and right sides. The mitral valve is located between the left atrium and right ventricle. The path of blood is from the pulmonary veins to the left atrium, and then to left ventricle finally leaving through the aorta and the rest of the body. If the mitral valve is malfunctioning by not closing fully, blood could only flow back into the left atrium as the mitral valve separates the left atrium and left ventricle. Note that the mitral valve is also known as the left atrioventricular valve, and the bicuspid valve.

A heart murmur is an extra or unusual sound heard during a heartbeat. It can be harmless or abnormal. A heart murmur is most often caused by heart valve disease and does not necessarily require treatment.

Endocarditis is an infection of the inner heart chambers and valves. It can also be used to describe an inflammation of the endocardium due to other problems. It is treated with antibiotics and can require surgery to remove or repair infected tissue.

Radiation is the correct answer because it describes the process by which pain from one area is transmitted to another. In this case it is because the heart's afferent nerve entry into the spinal cord is shared with the dermatomal sensory nerves of T1-T5. In particular T5 is located on the medial aspect of the upper arm (stopping at the elbow). Dislocation is when a joint becomes dislodge from its proper placement. Impingement occurs when a nerve or vessel (artery/vein) becomes compressed, typically related to an injury and causes pain. Fracture is the breaking of a bone. Phantom limb pain is felt by amputees in an amputated limb.

A patent ductus arteriosus (PDA) is a type of abnormal connection between the aorta and pulmonary artery. The ductus arteriosus is a normal vessel that is open during the fetal stage, but should close during birth. If the vessel remains open despite the pressure changes at birth, a left to right shunt occurs. It is termed a left to right shunt because blood will flow from the "left side of the heart" to the "right side of the heart" through the PDA. Blood through the heart flows from areas of high pressure to areas of low pressure. Because the aorta (left side of the heart) has higher pressure than the connected pulmonary artery (right side of the heart), blood tends to flow from the aorta to the pulmonary artery via a left-to-right shunt through the PDA.