Vasospasm: This is a common and likely cause of finger discoloration after heart catheterization. The procedure involves the insertion of catheters into the blood vessels, which can cause irritation and lead to vasospasm, resulting in reduced blood flow to the finger.

Thromboembolism: A blood clot forming in the catheterized vessel and traveling to the finger can cause discoloration due to ischemia. This is a plausible complication given the nature of the procedure.
Hematoma: Bleeding at the catheter site can lead to the formation of a hematoma, which may compress adjacent vessels and cause finger discoloration.
Arterial Dissection: Although less common, the catheterization process can cause a dissection in the arterial wall, leading to reduced blood flow and subsequent discoloration of the finger.

Aortic Dissection: Although rare, an aortic dissection is a life-threatening condition that could potentially occur during heart catheterization. It requires immediate recognition and treatment.
Cholesterol Embolization Syndrome: This condition, also known as "atheroembolism," can occur when the catheterization procedure dislodges cholesterol crystals from the aortic wall, leading to embolization in smaller vessels, including those supplying the fingers.

Raynaud’s Phenomenon: While not directly caused by catheterization, pre-existing Raynaud’s disease could be exacerbated by the procedure, leading to episodes of vasospasm and finger discoloration.
Buerger’s Disease (Thromboangiitis Obliterans): A rare disease of the blood vessels that could potentially be exacerbated by the catheterization procedure, leading to ischemic symptoms including finger discoloration.
Vasculitis: Inflammation of the blood vessels, which could be triggered by the catheterization procedure in rare cases, leading to reduced blood flow and discoloration of the affected areas.