There is no good evidence for what type of workup an asymptomatic hypertensive patient should get in the ED.  An ECG is likely to show LVH, a cxr will be normal in most cases, and many patients will have some degree of proteinuria.

So, what is a safe and reasonable strategy to workup these patients?

• Consider checking a serum creatinine. I say consider because even this recommendation isn't terribly evidence-based. Elevated creatinine may NOT indicate that a hypertensive emergency is present, but if the creatinine is elevated it might persuade you to choose a different antihypertensive agent (HCTZ won't lower BP effectively if the creatinine near 2.0, and many of us would be a little hesitant to start an ACE-I if the creatinine is elevated). Although there is one study that showed absence of proteinuria and hematuria was correlated with a normal serum creatinine, many patients with asymptomatic HTN will have proteinuria.
• Repeat the BP several times. One study has shown that as many as 1/3 of patients with high BP in the ED do not have elevated BP when followed up as an outpatient. Many patients' BPs will spontaneously decline (regression to the mean).
• In the asymptomatic patient a CXR and ECG will likely not help you manage a patient, so don't waste your time and the patient's money getting it.

American College of Emergency Physicians 2006 Guidelines on the evaluation of asymptomatic HTN.