Cardiac Ischemia or Infarction: This condition can lead to both shortness of breath due to heart failure and bradycardia due to ischemia affecting the heart's conduction system. Given the age and symptoms, cardiac issues are a primary concern.

Pulmonary Embolism: This can cause sudden onset of shortness of breath and, in some cases, bradycardia, especially if there's a large clot obstructing blood flow, leading to a decrease in cardiac output.
Chronic Obstructive Pulmonary Disease (COPD) Exacerbation: While COPD typically presents with tachycardia, severe cases can lead to bradycardia due to respiratory failure and hypercapnia.
Pneumonia: Severe pneumonia can cause both shortness of breath and, in some cases, bradycardia, particularly if the patient is elderly or has a compromised immune system.

Pulmonary Hypertension: This condition can lead to right heart failure, presenting with shortness of breath and potentially bradycardia due to increased pressure on the right side of the heart.
Cardiac Tamponade: Although less common, cardiac tamponade can cause both shortness of breath and bradycardia due to the compression of the heart, which impairs its ability to fill and pump blood effectively.
Hypothyroidism: Severe, untreated hypothyroidism can lead to respiratory and cardiac complications, including shortness of breath and bradycardia.

Amyloidosis: A rare condition where abnormal proteins (amyloid) accumulate in organs, potentially affecting the heart and lungs, leading to shortness of breath and bradycardia.
Sarcoidosis: An autoimmune disease that can affect multiple organs, including the lungs and heart, potentially causing shortness of breath and cardiac arrhythmias, including bradycardia.
Histiocytosis: A rare disease where abnormal immune cells accumulate in various tissues, potentially affecting the lungs and heart, leading to symptoms like shortness of breath and bradycardia.