A 44-year-old woman presents with a 3-year history of color changes in her fingers in cold weather, during which they turn white, then blue, then red. Over the past year, she has noticed progressive tightening of the skin over her fingers and backs of both hands, and has developed small, dilated blood vessels across her cheeks and lips. She has no difficulty raising her arms overhead or rising from a chair. Her skin tightening does not extend above the wrists. Examination confirms sclerodactyly, multiple telangiectasias on the face and anterior chest, and calcinosis at several fingertips. Serology returns ANA 1:640 centromere pattern; anti-centromere antibody positive; anti-Scl-70 negative.
Which of the following organ complications should be the primary focus of this patient's ongoing surveillance?