**Core Concept**
The patient's presentation of sudden onset shortness of breath, syncope, and skin lesions suggests a cardiac cause of her symptoms, likely related to a cardiac arrhythmia. This scenario requires consideration of conditions that can cause sudden cardiac death, often due to abnormal heart rhythms.

**Why the Correct Answer is Right**
The patient's ECG is likely to show evidence of a cardiac arrhythmia, such as a supraventricular tachycardia (SVT) or ventricular tachycardia (VT). Given the presence of skin lesions, the most likely diagnosis is a hypercoagulable state, specifically antiphospholipid syndrome (APS). APS can increase the risk of thrombosis, including cardiac thrombi that can precipitate arrhythmias and sudden cardiac death. The skin lesions are likely to be related to systemic lupus erythematosus (SLE), a common underlying condition in APS.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not directly related to the patient's symptoms and would not explain the skin lesions or cardiac arrhythmia.
**Option B:** While this condition can cause cardiac symptoms, it is less likely to be associated with skin lesions and would not be the primary diagnosis in this case.
**Option C:** This option is not a primary cardiac cause of sudden onset shortness of breath and syncope and would not explain the presence of skin lesions.
**Option D:** This option is a possible underlying condition but would not directly explain the patient's acute presentation of shortness of breath and syncope.

**Clinical Pearl / High-Yield Fact**
In patients with suspected cardiac arrhythmias, consider underlying hypercoagulable states, such as antiphospholipid syndrome, particularly if there are associated skin lesions. This is a classic exam trap, as many students focus solely on cardiac causes without considering systemic conditions that can contribute to cardiac symptoms.

**Correct Answer:** A. Antiphospholipid syndrome.