Stylized heart illustrating systolic and diastolic phases with SD ratio graph.

Is Your Heart in Sync? The Hidden Risks of Unbalanced Heart Rhythms in Pulmonary Hypertension

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Theo Raines in Health & Wellness October 2026 • 5 min read.

"Discover how a simple measurement, the systolic to diastolic duration ratio, can predict mortality in pulmonary hypertension and what it means for your heart health."


Pulmonary hypertension (PH) places increased strain on the right side of the heart, leading to potential dysfunction. Understanding the factors that contribute to right ventricular (RV) performance is essential for managing this condition. Recent research highlights the significance of the systolic to diastolic duration ratio (SD ratio) as a predictor of mortality in idiopathic pulmonary arterial hypertension (IPAH).

Echocardiography, a non-invasive imaging technique, is instrumental in evaluating heart function. The SD ratio, derived from tricuspid regurgitation Doppler, reflects the balance between the heart's contraction (systole) and relaxation (diastole) phases. An elevated SD ratio suggests RV dysfunction and has been linked to poorer outcomes in Eisenmenger syndrome and pediatric PAH.

This article explores how the SD ratio can serve as a valuable tool for assessing disease severity and predicting mortality in adults with IPAH. We'll delve into the findings of a study that investigated the predictive power of the SD ratio and its changes in response to pulmonary vasodilator therapies, offering insights into managing this challenging condition.

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Burden and Right-Heart Impact

A 2024 analysis searched the Global Index Medicus and PubMed for population-representative data on clinically diagnosed pulmonary arterial hypertension (PAH) published between 1980 and 2021, focusing on prevalence, incidence, and mortality. In PAH, the right-ventricular systolic-to-diastolic duration ratio reflects global right-ventricular performance, although its application in adults with non-congenital PAH has been limited. This highlights both the importance of measuring disease burden and the need for practical indicators of right-heart function.

From Screening to Confirmation

Right-heart catheterization remains the gold standard for assessing pulmonary hemodynamics, but its invasive nature has increased interest in non-invasive imaging. Two-dimensional transthoracic echocardiography is widely used as the primary screening tool for estimating the likelihood of pulmonary hypertension. Echocardiographic evaluation also includes guideline-recommended two-dimensional parameters intended to inform physiological assessment, prognosis, and clinical decision-making. In idiopathic PAH, researchers have additionally measured the systolic-to-diastolic duration ratio on echocardiograms to examine response to pulmonary vasodilator therapy and prognostic value at diagnosis and follow-up.

A Gradual Shift in Understanding

The understanding of pulmonary hypertension has developed through successive advances in hemodynamic assessment, cardiac imaging, and recognition of right-ventricular involvement. Earlier approaches emphasized identifying elevated pulmonary pressures, while contemporary perspectives increasingly consider how pressure overload affects the heart's timing and performance. This historical progression is best viewed as an ongoing refinement rather than a completed account of the disease.

The SD Ratio: A Window into Heart Health in Pulmonary Hypertension

Stylized heart illustrating systolic and diastolic phases with SD ratio graph.

A study published in the European Heart Journal examined the predictive value of the SD ratio in 74 patients diagnosed with IPAH. Researchers measured SD ratios using echocardiography at the time of diagnosis and during follow-up while patients were undergoing treatment with pulmonary vasodilator therapies. The goal was to determine if the SD ratio could accurately forecast mortality in this patient population.

Here's what the research revealed about the SD ratio and its connection to heart health in IPAH:

  • Static SD Ratio: The mean SD ratio at baseline was 0.97±0.29, remaining relatively unchanged at 0.93±0.26 during follow-up (p=0.86). This suggests that the SD ratio, once established, tends to be a stable indicator of heart function.
  • Correlation with RV Diameter: The SD ratio showed a weak correlation with basal RV diameter (r=0.25, p=0.03), indicating a potential link between RV size and the balance of systolic and diastolic durations.
  • Predictive of Mortality: Over a median follow-up of 5.6 years, 13 patients died. The SD ratio measured at diagnosis was significantly associated with an increased risk of death (HR 4.96, 95% CI: 1.12-21.88, p=0.03). This highlights the SD ratio's power as a prognostic marker.
  • Improved Prediction with Age: Including age in the analysis further enhanced the predictive value of the regression model (p<0.01), suggesting that age and SD ratio together provide a more comprehensive assessment of risk.
  • Trend Towards Increased Survival: Kaplan-Meier survival estimates suggested a trend towards increased survival in patients with lower SD ratios (Logrank p=0.12), although this finding didn't reach statistical significance.
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Research Continues to Evolve

Current research and reviews continue to examine how pulmonary hypertension should be detected, characterized, and monitored. The field is moving toward approaches that combine hemodynamic assessment with imaging and measures of right-heart performance. Because evidence and techniques remain under development, findings should be interpreted in the context of the specific patient population and study design.

Limits of Current Measures

A 2026 New England Journal of Medicine report describes heart-failure-related pulmonary hypertension as potentially driven by sympathetic overactivation, increased pulmonary vascular resistance, and right-heart effects, underscoring that mechanisms may differ across patients. Evidence for the right-ventricular systolic-to-diastolic duration ratio comes from studies measuring its response to pulmonary vasodilator therapy and its prognostic value in idiopathic PAH, but that evidence does not establish universal usefulness across all forms of pulmonary hypertension. Hemodynamic risk markers also require careful interpretation because some foundational observations about elevated mean pulmonary artery pressure came from patients with end-stage PAH, a distinct and uncommon subgroup.

Comparing Cardiac Timing Measures

Comparative research has examined left-ventricular eccentricity index and the tricuspid-valve systolic-to-diastolic ratio in infants at risk for bronchopulmonary dysplasia and pulmonary hypertension. Separate work has evaluated the right-ventricular systolic-to-diastolic ratio as a predictor of mortality in contemporary adult idiopathic PAH cohorts. These studies address related timing and remodeling concepts, but they involve different populations, including infants at risk for disease and adults with established idiopathic PAH. Their results therefore should not be treated as directly interchangeable.

These findings suggest that a prolonged SD ratio at diagnosis is indicative of RV dysfunction in IPAH and can serve as a predictor of mortality in contemporary patients. Monitoring the SD ratio could help identify high-risk individuals who may benefit from more aggressive interventions.

Taking Control of Your Heart Health: What the SD Ratio Means for You

Understanding your heart's systolic to diastolic duration ratio can empower you to take a more proactive role in managing your pulmonary hypertension. While the SD ratio is just one piece of the puzzle, it provides valuable insights into your heart's function and potential risks.

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A More Complete Clinical Picture

A balanced interpretation of pulmonary hypertension requires more than a single pressure measurement or rhythm-related index. Hemodynamics, imaging, right-ventricular performance, disease subtype, and clinical context each contribute to assessment. The available material supports a cautious synthesis: newer measures may add useful information, but they should complement rather than replace established clinical evaluation.

Projecting the PAH Burden

Research using the Global Burden of Disease 2021 database is analyzing global pulmonary arterial hypertension burden and trends from 1990 through 2021, with projections extending to 2050. A separate 2026 report focuses on the disproportionate PAH burden among older adults and examines global, regional, and national trends from 1990 to 2021. Recent reviews also describe PAH as a rare, progressive disease involving fibroproliferative vascular remodeling, increased pulmonary vascular resistance, right-ventricular failure, and premature death. Together, these efforts point toward future work that combines long-term population projections with more detailed biological and clinical characterization.

Complex Evidence, Complex Care

One major challenge in pulmonary hypertension management is heterogeneity among studies, including differences in non-pharmacological interventions and pulmonary hypertension subtypes. The expanding volume of global clinical research also makes it harder for clinicians and researchers to synthesize emerging evidence and identify meaningful trends. Proposed measures such as the pulmonary-systemic pulse pressure ratio are being studied for associations with mortality in PAH, but such associations must be interpreted within the broader complexity of the evidence base.

From Guidelines to Daily Life

Real-world research is assessing whether guideline-recommended, risk-based treatment approaches influence outcomes for patients with incident pulmonary arterial hypertension. One study compares all-cause mortality across risk groups and among patients receiving monotherapy, dual therapy, or triple therapy across risk strata. Patient-reported research from the multinational Adelphi Disease Specific Programme examines how people with PAH experience the diagnostic process. Echocardiography case-study material further illustrates its role in assessing disease progression and hemodynamic consequences.

If you have been diagnosed with IPAH, discuss the SD ratio with your cardiologist. Ask about incorporating echocardiography and SD ratio measurements into your routine monitoring. This information can help your doctor personalize your treatment plan and make informed decisions about your care.

By staying informed and actively participating in your healthcare, you can optimize your heart health and improve your overall well-being despite the challenges of pulmonary hypertension. Remember, knowledge is power, and a deeper understanding of your condition can lead to better outcomes.

The ratio differed from controls and fell at follow-up

  • 0.18In a separate adult idiopathic PAH cohort, the mean ratio fell from 1.03 at diagnosis to 0.85 at follow-up, a decrease of 0.18 over a median interval of 9.0 months.[1]

What the timing measure can tell us

A higher ratio was associated with poorer right-ventricular function on echocardiography, worse catheterization hemodynamics, shorter walking distance, and worse clinical outcomes. This convergence suggests the timing measure tracks several aspects of disease severity, but an association does not establish that it causes those outcomes.[2]

The measure is intended to reflect overall right-ventricular performance, but its evidence base in adults with non-congenital PAH has been limited. Its interpretation therefore depends on the population and measurement conditions, rather than establishing a universal marker for pulmonary hypertension.[1]

How the ratio compares with other heart measures

A meta-analysis identified pericardial effusion, right atrial area, and tricuspid annular plane systolic excursion among the best-investigated robust predictors of mortality or transplant in PAH. This establishes their prognostic evidence, but does not show whether they add to or replace the timing ratio.[3]

An umbrella review also reports prognostic value for pericardial effusion, right atrial area, and tricuspid annular systolic displacement, as well as independent prognostic value for right-ventricular longitudinal strain. These findings place the ratio among a broader set of echocardiographic measures; they do not establish a ranking between them.[4]

Echocardiographic estimates can rely on assumptions, and severe tricuspid regurgitation may compromise their accuracy. The evidence describes this as a general concern for echocardiographic parameters; it does not report the ratio’s accuracy specifically under severe regurgitation.[5]

Echocardiography is operator-dependent, so agreement between imaging and another assessment can be affected by the operator’s experience. This is a measurement consideration, not evidence about how much the ratio contributes to prognosis.[5]

In severe tricuspid regurgitation, peak velocity may underestimate pressure gradients; high cardiac output or artifacts may instead lead to overestimation. These examples show why pressure estimates also depend on the conditions and signals being measured.[5]

Right-ventricular diastolic assessment integrates information from different echocardiographic views and modalities. That broader approach cautions against treating any single measure as a complete account of heart function.[6]

What remains uncertain about the duration ratio

  • Does the ratio retain its relationship with outcomes across different pulmonary hypertension subgroups, given the limited evidence in adults with non-congenital PAH?[1]
  • How reliable is the ratio when echocardiographic assumptions are challenged by severe tricuspid regurgitation or operator-dependent measurement? The cited material identifies these potential sources of uncertainty but does not quantify their effect on the ratio itself.[5]

Sources

  1. Right ventricular systolic to diastolic duration ratio: A novel predictor of outcome in adult idiopathic pulmonary arterial hypertension. (pubmed.ncbi.nlm.nih.gov)
  2. Usefulness of the right ventricular systolic to diastolic duration ratio to predict functional capacity and survival in children with pulmonary arterial hypertension. (pubmed.ncbi.nlm.nih.gov)
  3. Echocardiographic findings associated with mortality or transplant in patients with pulmonary arterial hypertension: A systematic review and meta-analysis (pmc.ncbi.nlm.nih.gov)
  4. Diagnostic and prognostic value of echocardiography in pulmonary hypertension: an umbrella review of systematic reviews and meta-analyses. (pubmed.ncbi.nlm.nih.gov)
  5. The Role of Echocardiography in the Diagnosis and Prognosis of Pulmonary Hypertension (pmc.ncbi.nlm.nih.gov)
  6. Echocardiographic assessment of the right heart in adults: a practical guideline from the British Society of Echocardiography (pmc.ncbi.nlm.nih.gov)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

1

What is the systolic to diastolic duration ratio (SD ratio), and why is it important in pulmonary hypertension?

The systolic to diastolic duration ratio, or SD ratio, is a measurement derived from echocardiography, specifically tricuspid regurgitation Doppler, that reflects the balance between the heart's contraction (systole) and relaxation (diastole) phases. It is used to assess right ventricular function, especially in the context of pulmonary hypertension. An elevated SD ratio may indicate right ventricular dysfunction.

2

How is the systolic to diastolic duration ratio (SD ratio) measured, and what does it tell doctors about heart function?

The SD ratio is determined through echocardiography. During this non-invasive imaging procedure, the duration of systole and diastole are measured, and the ratio between them is calculated. This measurement provides insights into how effectively the heart is pumping blood and relaxing between beats, particularly concerning the right ventricle's function in patients with pulmonary hypertension.

3

How does the systolic to diastolic duration ratio (SD ratio) relate to survival rates in individuals with idiopathic pulmonary arterial hypertension (IPAH)?

Research indicates that an elevated SD ratio at the time of diagnosis is associated with an increased risk of mortality in patients with idiopathic pulmonary arterial hypertension (IPAH). Specifically, a study showed a significant association between the SD ratio and mortality, highlighting its role as a prognostic marker. Monitoring this ratio can help identify high-risk individuals who may benefit from more aggressive treatment strategies.

4

Is the systolic to diastolic duration ratio (SD ratio) the only factor to consider when assessing heart health in pulmonary hypertension?

While the SD ratio offers valuable insights into right ventricular function and prognosis in IPAH, it is essential to consider it alongside other clinical assessments. Factors such as age, the severity of pulmonary hypertension, and response to pulmonary vasodilator therapies also play crucial roles in determining overall patient outcomes. A comprehensive evaluation, including the SD ratio, helps provide a more accurate assessment of risk and guides personalized treatment decisions. The study also mentions correlation with the basal RV diameter.

5

Beyond idiopathic pulmonary arterial hypertension (IPAH), in what other conditions might the systolic to diastolic duration ratio (SD ratio) be a relevant measurement?

The study published in the European Heart Journal focused on patients with idiopathic pulmonary arterial hypertension (IPAH). The relevance of the systolic to diastolic duration ratio (SD ratio) may extend to other forms of pulmonary hypertension or heart conditions where right ventricular dysfunction is a concern, such as Eisenmenger syndrome and pediatric PAH. Further research is needed to establish its utility and predictive value in these different contexts. The SD ratio's applicability in various populations could broaden its use as a valuable tool for assessing heart health.

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