What is the diagnostic approach for orthostatic hypotension?

Diagnostic Approach for Orthostatic Hypotension

The definitive diagnostic approach for orthostatic hypotension requires measuring blood pressure in both supine and standing positions, with a sustained decrease in systolic BP ≥20 mmHg, diastolic BP ≥10 mmHg, or a decrease in systolic BP to <90 mmHg within 3 minutes of standing. 1, 2

Definition and Diagnostic Criteria

• Classical orthostatic hypotension (OH) is defined as a sustained decrease in systolic BP ≥20 mmHg, diastolic BP ≥10 mmHg, or a decrease in systolic BP to <90 mmHg within 3 minutes of standing or head-up tilt of at least 60 degrees 1, 2
• In patients with supine hypertension, a larger systolic BP drop ≥30 mmHg should be considered diagnostic 1
• Initial OH is characterized by BP decrease >40 mmHg systolic or >20 mmHg diastolic within 15 seconds of standing, with spontaneous recovery within 40 seconds 1
• Delayed OH occurs beyond 3 minutes of standing, characterized by a slow progressive decrease in BP 1, 3

Proper Measurement Technique

• Patient should rest in supine or sitting position for 5 minutes before baseline BP measurement 2
• Use validated and calibrated devices with appropriate cuff size 1, 2
• Measure BP in both arms at the initial visit, and use the arm with higher BP (if difference >10 mmHg) for subsequent measurements 1, 2
• After baseline measurement, perform follow-up measurements at 1 minute and 3 minutes after standing 2
• Maintain the arm at heart level during all measurements 2
• For accurate diagnosis, the patient should be fasted for 3 hours before the test and avoid nicotine and caffeine 4

Testing Methods

• Bedside orthostatic vital sign measurement (simplified Schellong test) is the primary diagnostic approach 5
• Head-up tilt-table testing can aid in confirming a diagnosis when standard orthostatic vital signs are nondiagnostic 6
• Continuous BP monitoring is preferable to interval BP measurement for detecting OH, particularly for initial OH 7, 8
• Testing should be performed in a temperature-controlled environment (21-23°C) 4

Patterns and Classification

• Observe the pattern of BP decrease:
  • Classical OH shows a "concave" curve of BP decrease immediately after standing 4
  • Delayed OH shows a more variable pattern of decrease occurring after 3 minutes 4
• Assess heart rate response to classify as:
  • Neurogenic OH: blunted heart rate response (<10 beats per minute increase) indicates autonomic dysfunction 3
  • Non-neurogenic OH: preserved or enhanced heart rate increase as a compensatory mechanism 3

Differential Diagnosis

• Drug-induced autonomic failure (most frequent cause of OH) - particularly diuretics, vasodilators, and alcohol 4
• Neurogenic causes: primary autonomic failure (Parkinson's disease, multiple system atrophy) and secondary autonomic neuropathies (diabetes, amyloidosis) 2
• Non-neurogenic causes: hypovolemia, cardiac insufficiency, impaired venous return 9
• Situational syncope: associated with specific scenarios (micturition, coughing, defecating) 4
• Postural orthostatic tachycardia syndrome (POTS): excessive heart rate increase without significant BP drop 3

Additional Diagnostic Considerations

• Echocardiography may be used if cardiac cause is suspected 2
• ECG should be used to rule out arrhythmias that may contribute to symptoms 2
• 24-hour ambulatory blood pressure monitoring can detect patterns of BP variability 2
• Consider delayed OH by extending standing time beyond 3 minutes if symptoms suggest OH but initial testing is negative 2

Common Pitfalls and Caveats

• Poor reproducibility when testing for OH - consider repeated measurements if clinical suspicion is high 7
• Failure to recognize neurogenic OH may lead to inappropriate treatment strategies 3
• Pseudohypertension in elderly patients with calcified arteries may lead to overtreatment and iatrogenic OH 2
• Symptoms depend more on the absolute BP level than the magnitude of the fall 1, 2
• OH is associated with increased mortality, cardiovascular disease prevalence, and fall risk 1, 3