Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (62 page)

   Genetic evaluation for suspected cases of Brugada syndrome (SCN5A mutations) and catecholaminergic polymorphic ventricular tachycardia (RyR2 gene) has high yield and may impact clinical treatment and recommendations to patients and family members.

Suggested Readings

Bai R, Napolitano C, Bloise R, et al. Yield of genetic screening in inherited cardiac channelopathies: how to prioritize access to genetic testing.
Circ Arrhythm Electrophysiol.
2009;2:6–15.

Priori SG, Blomstrom-Lundqvist C, et al. Update of the guidelines on sudden cardiac death of the European Society of Cardiology.
Eur Heart J.
2003;24:13–15.

HYPERTENSION

   Definition

   The NHANES national survey from 2005 to 2008 estimates that 30% of adults in the United States have hypertension, and most (>90%) have essential or primary hypertension.

   An individual is considered to have hypertension based on the average of two or more blood pressure readings following an initial assessment (Table
3-1
).

   Using ambulatory blood pressure monitoring, a patient is hypertensive if average BP for 24 hours is above 135/85 mm Hg, daytime is >140/90 mm Hg, or nighttime is >125/75 mm Hg.

   
Secondary hypertension
is high BP caused by an identifiable and potentially curable disorder.

   
Hypertensive crisis
encompasses hypertensive urgency and emergency. Hypertensive urgency is DBP > 120 mm Hg with end-organ damage. Hypertensive emergency is acute or worsening end-organ damage associated with elevated BP, regardless of level. The term
malignant hypertension
is reserved for hypertensive emergency with papilledema or retinal hemorrhage.

   A 20 mm Hg increment of SBP or 10 mm Hg of diastolic BP in middle-aged and elderly persons is associated with a twofold increase in mortality from CVD throughout the BP range. This relationship is strongly correlated and continuous.

TABLE 3–1 Blood Pressure Classification Suggested by the Joint National Committee

The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.
Hypertension.
2003;42:1206.

   Who Should Be Suspected?

   Mild to moderate essential hypertension is usually asymptomatic. The physical exam and history should focus on the need for a secondary hypertension work up (including the degree of difficulty achieving acceptable BP control) and the presence and severity of end-organ damage.