Transient Ischemic Attack (TIA): Given the sudden onset of numbness and weakness in one arm without chest pain, a TIA is a plausible diagnosis. The absence of chest pain and the presence of a normal sinus rhythm on ECG make this more likely than an acute coronary syndrome, especially considering the patient's history of SVT and ablation, which might suggest a predisposition to arrhythmias or vascular events.

Anxiety or Panic Attack: The episode occurring at work and the absence of chest pain could suggest an anxiety or panic attack, especially if the patient has a history of anxiety disorders. However, the presence of numbness and weakness would need to be carefully evaluated to rule out more serious conditions.
Migraine with Aura: Some migraines can present with neurological symptoms such as numbness and weakness, and the absence of headache does not rule out this diagnosis, as some migraines can be acephalic (without headache).
Peripheral Neuropathy: Although less likely given the acute presentation, peripheral neuropathy could cause numbness and weakness, but it typically does not present as abruptly as described.

Acute Coronary Syndrome (ACS): Although the ECG shows a normal sinus rhythm and there's no chest pain, ACS, including myocardial infarction, must be considered, especially in women who may present atypically. The history of SVT and ablation might also indicate a need for careful cardiac evaluation.
Stroke: Similar to TIA, but with potentially more severe and lasting consequences. Immediate evaluation for stroke is crucial, given the symptoms of numbness and weakness.
Cardiac Arrhythmia: Given the patient's history of SVT and ablation, another arrhythmic event could be a cause of her symptoms, potentially leading to reduced cardiac output and subsequent neurological symptoms.

Multiple Sclerosis: An initial presentation of multiple sclerosis could include numbness and weakness, but this would be less likely given the acute onset and the specific distribution of symptoms to one arm.
Neurosyphilis: A rare condition that can cause a wide range of neurological symptoms, including numbness and weakness, but this would be an unusual diagnosis without other supporting evidence or risk factors.
Mitochondrial Myopathies: Rare genetic disorders that affect muscle and nerve cells, potentially causing weakness and numbness, but these conditions typically have a more gradual onset and are associated with other systemic symptoms.