The current study is designed to have broad generalizability and inform a potential shift toward greater utilization of stress echocardiography with UCA. This will be accomplished by comparing UCA stress echocardiography with myocardial SPECT among hospitalized patients presenting with atraumatic chest pain. This study seeks to demonstrate: clinical comparability of the 2 modalities (based on non-diagnostic test rates), improved care efficiency (based on length of stay), lower costs, improved provider satisfaction, and a presumed improved safety profile through the elimination of radiation exposure.

Primary Hypothesis: A strategy of routine UCA (Optison™) enhanced stress echocardiography will result in a clinically non-diagnostic test rate comparable to myocardial SPECT among patients hospitalized (inpatient or hospital observation status) with atraumatic chest pain.

Inclusion Criteria:

• Patients must meet all of the following inclusion criteria to be eligible for participation in this study:

  1. Males or females aged ≥ 18 years

  2. Evaluated for symptoms of chest discomfort or ischemic equivalent

  3. Clinical indication for stress imaging, defined as one of the following clinical risk estimates for CAD based upon the Diamond and Forrester classification7:

     • Intermediate pretest probability of CAD and electrocardiogram (ECG) is clinically interpretable and patient is able to exercise
     • Intermediate pretest probability of CAD and ECG is clinically interpretable or patient is unable to exercise
     • High pretest probability of CAD regardless of ECG interpretability and ability to exercise

  4. Willing and able to provide written informed consent to participate in this study

  5. Agrees to remain under observation (e.g., inpatient or observational status) until all study procedures from the hospital stay are completed, and to complete a 30-day follow up call

Exclusion Criteria:

• Patients who meet any of the following exclusion criteria are not to be enrolled in this study:

  1. Documented medical history or discovery during screening and/or admission of any of the following:

     • Severe aortic or mitral stenosis
     • Significant resting left ventricular outflow tract obstruction (velocity > 3 cm/s)
     • Mobile left ventricular apical thrombus
     • Acute pericarditis or pericardial tamponade
     • Ascending or thoracic aortic aneurysm that is not stable or meets surgical criteria
     • Acute decompensated congestive heart failure
     • Established severe left ventricular systolic dysfunction (left ventricular ejection fraction < 35%)

  2. Definite acute coronary syndrome (e.g., unstable angina, acute myocardial infarction) as confirmed by elevated Troponin I (>0.6 ng/L) on two successive measurements or ECG changes diagnostic for unstable angina (e.g. localized ST changes) in conjunction with clinical appraisal

  3. Any of the following other abnormalities on the ECG at screening:

     • Paced ventricular rhythm or complete left bundle branch block
     • Uncontrolled arrhythmias defined by frequent premature ventricular complexes (PVCs) > 10/minute, non-sustained ventricular tachycardia, or atrial fibrillation with rapid ventricular response
     • 2nd or 3rd degree heart block

  4. Uncontrolled hypertension defined as systolic blood pressure ≥ 200 mmHg and/or diastolic blood pressure ≥ 110 mmHg at screening

  5. Hemoglobin (Hb) < 7.5 mg/dL at screening or within 3 months prior to screening

  6. Potassium < 3.0 mmol/L or > 5.5 mmol/L or severe electrolyte abnormality at screening that, in the opinion of the supervising physician or Investigator, makes stress testing unsafe

  7. Females who are pregnant or nursing

  8. Known intolerance to any of the study stress agents (dipyridamole, dobutamine) or study cardiac imaging agents (Optison, Cardiolite)

  9. Weight ≥ 350lbs

  10. Any physical or psychological condition that, in the opinion of the Investigator, may adversely affect the safety of the patient if enrolled in this trial.