Professor Satish Raj and recent MSc graduate Nasia Sheikh provide an overview of initial orthostatic hypotension (IOH), how these patients present in the clinic, the mechanisms underlying the condition, and IOH management with a non-pharmacological approach.
- Characterization of IOH, a highly underrecognized disorder
- Therapeutic exploitation of the IOH refractory period
- Improvement of IOH symptoms through lower body muscle pre-activation and post-tensing
- Comparison of sympathetic activation and muscle contraction in symptom mitigation
- Patient experiences of living with IOH and quality of life improvement following treatment
Professor Raj begins this webinar by characterizing IOH and comparing its characteristics with other subsets of OH. Recent MSc graduate Nasia Sheikh further details the mechanisms that underlie IOH, how the condition can be managed with a non-pharmacological approach, and how the daily lives of individuals with IOH are affected by this condition.
“Not all orthostatic hypotension is the same.”
Classical OH (cOH) is defined by a drop in systolic blood pressure (SBP) and diastolic blood pressure (DBP) of at least 20 mmHg and 10 mmHg, respectively, within 3 minutes of passive or active standing. This condition is a significant problem in the elderly, and increases in frequency with age. In contrast, IOH is characterized by a large transient decrease in SBP and DBP of at least 40 mmHg and 20 mmHg, respectively, within 15 minutes of active standing. The consensus within the scientific community is that muscle activation is critical for IOH, since IOH occurs by rapid vasodilation in contracting leg muscles due to the brief muscular effort required to stand.
Although individuals with IOH experience symptoms that significantly affect their daily lives, IOH is a highly underrecognized condition. A recent study in 2018 found that the second most common form of unexplained syncope was IOH, and that it was a common reason for clinic visits. From his own experience, Professor Raj further notes that while IOH is a frequent reason for referrals, patients are often initially misdiagnosed or misreffered for syncope or postural orthostatic tachycardia syndrome (POTS).
“I’ve had patients, including physicians, … travel 10, 12 hours to see me in clinic to discuss this issue, and that speaks to the concern that they have and the impact that this has on their life.”
The speed of standing up is critical in the management of IOH. Literature suggests that individuals with IOH should sit up first before standing, if possible, or stand very slowly. Interestingly, individuals with IOH who feel so unwell that they must sit down again find that symptoms often do not reoccur after standing up for a second time. A proof-of-concept study conducted by the Raj group found that there is a two minute refractory period to the reflex underlying IOH, and that IOH response can be blunted with a short sit. The large SBP drop that occurs upon standing after two minutes of sitting is likely primarily due to a rapid decrease in systemic vascular resistance (SVR), and secondarily due to a decrease in stroke volume (SV).
A study was subsequently performed to determine if the refractory period could be exploited for treatment. The efficacy of lower body muscle pre-activation (LMBP) and lower body muscle post-tensing (LBMT) were explored as symptom management options for IOH. This study found that LBMP blunts IOH through an increase in cardiac output, while LBMT blunts IOH through a decrease in SVR and increase in SV. Both LBMP and LBMT could reduce presyncope symptoms upon standing.
A physiological study was conducted next to determine whether sympathetic nervous system activation or skeletal muscle contraction was more effective in mitigating the IOH response. While the drop in SBP was significantly reduced by both types of intervention, muscle contraction alone reduced presyncope symptoms. Therefore, muscle contraction may be more clinically relevant than sympathetic activation.
To provide a deeper understanding of IOH, the Raj group also conducted a qualitative study of the patient experience and their quality of life. This study aimed to assess the impact of IOH on the daily lives of patients, as well as the social, emotional, and financial implications of the condition. IOH has been found to negatively impact family life, social life, work, and mental health. Some patients even reported having to considerably adjust their lifestyle due to symptom burden, resulting in feelings of loss and a reduced quality of life.
“An important theme that arose from this study was that participants felt that IOH was an invisible disorder.”
Participants in this study revealed that the invisibility of their condition made it difficult to discuss symptoms with their family, friends, and even physicians, and prevented some from seeking help when symptoms began. Since IOH is an underrecognized disorder, many patients must seek multiple physicians to receive a diagnosis. In fact, an official diagnosis was one of the most important things reported by participants in their journey with IOH since it not only validated their experience, but provided them with an understanding of what they were experiencing. With a diagnosis and treatment plan, patients with IOH are able to begin IOH management and return to their normal lives.
In conclusion, Nasia Sheikh notes that future directions in this work will include determining if there are sex-specific differences in the refractive period and underlying mechanisms of IOH, as well as assessing the efficacy of combining LBMP and LBMT to further ameliorate IOH symptoms. Increased awareness of IOH is critical in improving the overall patient experience and reducing burden on the healthcare system, as the quick and accurate diagnosis of IOH can decrease the number of clinic visits.
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- Doesn’t IOH just happen to everybody every once in a while?
- Can IOH be used as a proxy marker of sympathetic tone?
- Is fluid status relevant to IOH?
- Since IOH is so transient, could it be detected with manual BP cuffs?
- What is the severity of IOH in type 2 diabetes patients?
- Is it possible to modify the testing protocol to evaluate patients who cannot stand?
- Is OH part of a syndrome similar to POTS?
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Professor of Cardiac Science
School of Medicine
University of Calgary
Student Clinical Researcher
Cardiovascular & Respiratory Sciences
University of Calgary