Why are heart failure symptoms predominantly pulmonary?

In heart failure, particularly left-sided heart failure, the backing up of blood into the pulmonary circulation is a primary reason for the development of pulmonary symptoms. When the left ventricle is unable to effectively pump blood forward to the systemic circulation, it results in an increase in left ventricular end diastolic pressure. This elevated pressure is transmitted backwards into the pulmonary veins and capillaries, causing pulmonary congestion and edema. The accumulation of fluid in these areas leads to symptoms such as shortness of breath (dyspnea), orthopnea (difficulty breathing while lying flat), and paroxysmal nocturnal dyspnea (sudden nighttime breathlessness).

The other choices do not accurately explain why pulmonary symptoms dominate in heart failure. Low blood pressure might occur in heart failure but does not directly cause pulmonary symptoms. Decreased lung capacity could result from various lung diseases but is not the central mechanism in heart failure-related pulmonary symptoms. Isolated right heart failure typically leads to systemic venous congestion and peripheral symptoms, rather than primarily affecting the pulmonary circulation. Thus, the correct answer highlights the critical link between left ventricular dysfunction and elevated pressures within the pulmonary circulation, leading to the characteristic pulmonary symptoms in heart failure.