1. Unusual Fatigue Extreme, unexplained fatigue is a common early sign, especially for women. Exhaustion despite adequate sleep. Severe tiredness from simple tasks. Fatigue that doesn’t improve with rest. 2. Shortness of Breath, Breathing difficulties can signal heart trouble. Shortness of breath during light activity or rest. Dizziness or lightheadedness. Trouble breathing when lying down. 3. Chest Pain Chest pain is a well-known symptom, but it may not appear as expected. Pressure, tightness, or aching. Pain radiating to arms, back, neck, or jaw