CARDIOVASCULAR IMAGING AND STRESS TESTING

Despite continuing advances that have greatly expanded the ability to assess cardiovascular anatomy noninvasively through an array of imaging modalities, chest radiography (CR) remains a very useful part of the initial cardiovascular evaluation. CR is widely available, can be acquired rapidly and inexpensively, and has a low associated ionizing radiation dose. With an organized approach toward interpretation, and insight into the strengths and limitations of CR, the cardiologist can maximize the use of this tool in clinical practice. This chapter focuses on the most important components of the CR with regard to cardiovascular disease, namely:

The following radiographs illustrate the appearance of a variety of cardiac abnormalities. Whenever possible, tables are included to delineate the differential diagnoses for representative chest radiographic findings.

BASIC APPROACH AND PROJECTIONS

Understanding the strengths and weaknesses of CR techniques is helpful in both the selection and interpretation of exam. Standard CR techniques include erect posteroanterior (PA) and lateral projections. In patients unable to stand for an erect PA, an anteroposterior (AP) radiograph can be performed. Additional specialized CR techniques exist, though their utilization is limited with widespread availability of tomographic imaging. The erect PA and lateral technique hold several advantages, as AP technique will magnify car- diomediastinal structures, and the ability to interpret pulmonary vasculature correctly is limited in supine patients. Additionally, more standardized techniques of acquisition are often used with PA radiographs, allowing for more reliable comparison between radiographs. Benefits of portable radiographs include the speed and convenience of obtaining a radiograph without transporting a patient.

Interpretation of radiographs can be aided by an ordered approach. Identification of the patient’s name and date of the examination is a straightforward but important step and can save further confusion or wasted time when checked first. Visible medical devices (catheters, drains, and other support devices) should be assessed to confirm position and any associated complication. When prior CRs are available, they should be assessed concurrently to help detect new abnormalities or to confirm the stability of a long-standing finding.

The three aforementioned components, pulmonary vasculature, cardiomediastinal silhouette, and calcifications, can then be reviewed in any order. Changes in each of these central components are a direct manifestation of the underlying cardiovascular disorder; and taking all three of these components into account ensures an appropriate, systematic approach to the standard CR. Other elements of CR interpretation are important (such as appropriate technique, assessment of pulmonary parenchyma) and have important clinical implications; however, we focus our discussion toward the elements most helpful in depiction of cardiovascular disease.

PULMONARY VASCULAR PATTERNS

Pulmonary Vascular Patterns in Normal and Various Cardiovascular Disease States

Decreased Pulmonary Blood Flow (Fig. 8.1)

Increased Pulmonary Blood Flow (Fig. 8.2)

Increased distributed (Fig 8.3)

Pulmonary Arterial Hypertension (PAH)

Causes of PAH

Increased: Central (Fig. 8.4)

Pulmonary Venous Hypertension

Stages of PVH

Stage 1: Pulmonary vascular redistribution

PCWP: Acute, 13 to 18 mm Hg; chronic, 18 to 22 mm Hg

Stage 2: Redistribution + interstitial pulmonary edema

PCWP: Acute, 18 to 25 mm Hg; chronic, 23 to 30 mm Hg

Stage 3: Redistribution + interstitial and alveolar pulmonary edema

PCWP: Acute, >25 mm Hg; chronic, >30 mm Hg>

Causes of PVH

Pulmonary venoocclusive disease

Pulmonary vein stenosis (postradiation therapy, post–atrial fibrillation ablation)

Left atrial/left ventricular obstruction

Myxoma or other tumors

Mitral valve disease

Mitral stenosis

Mitral regurgitation

Left ventricular compromise

Dilated cardiomyopathy

Acute or chronic myocardial ischemic disease

Restrictive cardiomyopathy

Pericardial disease

Constrictive pericarditis

Pulmonary Edema Patterns

Increased hydrostatic pressure gradient

Increased capillary permeability

Decreased osmotic pressure gradient

Lymphatic incompetence