Background: Guidelines recommend consideration of an ischemic evaluation (Class IIa-IIb) in new-onset heart failure (HF), but it is not well-known how often this is performed and leads to revascularization. Objectives: The authors investigated temporal trends in ischemic evaluation and revascularization within 90 days of HF onset in Denmark 2008-2018. Methods: From the Danish nationwide administrative registries, diagnostic tests and revascularizations within 90 days were identified among patients with new-onset HF between 2008 and 2018, alive 90 days after diagnosis. Results: Of 61,475 patients (mean age: 72.6 ± 13.8 years, 46% women), 12,503 (20%) underwent an ischemic evaluation, of whom 10,547 (84%) underwent invasive coronary angiography, and 1,956 (16%) underwent an initial noninvasive test, most frequently coronary computed tomographic angiography (n = 1,813, 93%). Of those who were initially referred for coronary computed tomographic angiography, 374 (21%) had a subsequent invasive coronary angiogram undertaken. Among individuals undergoing ischemic testing, percutaneous coronary intervention and coronary artery bypass graft surgery were performed in 1,354 (11%) and 619 (5%), respectively, corresponding to 2.2% and 1.0% of the entire sample. Between 2008 and 2018, the number of patients referred for ischemic evaluations increased, adjusted OR for 1.07 (95% CI: 1.06-1.07) per year high, and was greater among older versus younger individuals (OR: 1.01 [95% CI: 0.99-1.03], OR: 1.04 [95% CI: 1.03-1.06], OR: 1.06 [95% CI: 1.05-1.07], OR: 1.11 [95% CI: 1.09-1.12], and OR: 1.14 [95% CI: 1.10-1.18] per year increase for age group <50, 51-60, 61-75, 76-85, and >85 years, respectively, P for interaction <0.0001). Conclusions: In clinical practice, few patients with new-onset HF are referred for an ischemic evaluation and a minority undergo revascularization. Studies are needed to establish the appropriateness of this practice.