Fluorouracil - has there been any noted cardiac effects such as tachycardia and PVC's in patients on

Yes...
This from http://www.drugs.com/sfx/fluorouracil-side-effects.html

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"... Cardiac side effects associated with fluorouracil therapy are characterized by chest pain, arrhythmia, and electrocardiogram (ECG) changes. ECG changes consisted of diffuse ST segment elevations (or depression), tall peaked T waves, T-wave inversions, and sinus tachycardia. Other changes seen include prolongation of the QT interval, atrial fibrillation, ventricular extrasystoles, sustained and nonsustained ventricular tachycardia, and ventricular fibrillation. In some patients, chest pain was accompanied by ECG and serum enzyme changes suggestive of myocardial ischemia. Studies suggest the incidence of cardiac toxicity to be less than 10%. Cardiac toxicity has been observed with both the bolus and infusional schedules; however, is more common with the continuous infusion. A case of late-onset severe cardiotoxicity from fluorouracil therapy resulting in death has been reported.

The mechanism of cardiac toxicity with fluorouracil is unknown but proposed mechanisms include direct toxicity to the myocardium, coronary vasospasm, autoimmune phenomena, and thrombogenic effects. Another theory has suggested an impurity, fluoroacetaldehyde, generated in the alkaline solution of fluorouracil vials during storage which may be converted to a cardiotoxic substance, fluoroacetate. "