From the Guidelines
A transpulmonary gradient (TPG) of 9 mmHg is generally considered within normal limits, indicating no significant pulmonary vascular resistance beyond what would be expected from left heart pressures. TPG is calculated as the difference between mean pulmonary artery pressure (mPAP) and pulmonary capillary wedge pressure (PCWP), and values below 12 mmHg are typically considered normal 1. A TPG of 9 mmHg suggests that any pulmonary hypertension present is likely passive, resulting from left heart disease rather than from intrinsic pulmonary vascular disease.
In clinical practice, this would suggest that treatment should focus on managing the underlying left heart condition rather than targeting pulmonary vasculature specifically. The normal TPG indicates that the pulmonary vasculature is able to accommodate the cardiac output without developing excessive resistance, which is physiologically favorable. However, interpretation should always consider the complete hemodynamic profile and clinical context of the individual patient. Some studies have suggested that a TPG >12 mmHg is indicative of intrinsic changes in the pulmonary circulation 1, but a value of 9 mmHg is below this threshold.
It's worth noting that the definition and interpretation of TPG can vary depending on the context and population being studied. For example, in patients with single-ventricle physiology, a TPG >6 mm Hg has been suggested as predicting high risk for poor outcomes 1. However, in the general population, a TPG of 9 mmHg is not considered abnormal. The most recent and highest quality study on this topic is from 2015, which recommends using a combination of diastolic pulmonary gradient (DPG) and pulmonary vascular resistance (PVR) to define the different types of pulmonary hypertension due to left heart disease 1.
Key points to consider when interpreting a TPG of 9 mmHg include:
- The TPG is within normal limits, suggesting no significant pulmonary vascular resistance
- The pulmonary hypertension present is likely passive, resulting from left heart disease
- Treatment should focus on managing the underlying left heart condition
- Interpretation should consider the complete hemodynamic profile and clinical context of the individual patient.
From the Research
Transpulmonary Gradient (TPG) of 9
- A transpulmonary gradient (TPG) is used to assess the severity of pulmonary hypertension related to left-sided heart disease 2.
- TPG is calculated as the difference between the mean pulmonary artery pressure and the pulmonary capillary wedge pressure.
- A TPG of 9 is below the threshold of 12 mmHg, which is historically used to identify patients with pulmonary artery remodeling and 'out of proportion' pulmonary hypertension 2.
- However, a study suggests that a diastolic pulmonary gradient (DPG) ≥ 7 mmHg may be a superior indicator of worse clinical function and prognosis 2.
- The clinical significance of a TPG of 9 is not explicitly stated in the available evidence, but it can be inferred that it may not be as severe as a TPG above 12 mmHg.
- Further evaluation of the patient's clinical parameters, such as 6-min walk distance, cardiac output, and right atrial pressure, is necessary to determine the severity of the condition 2.
Related Concepts
- Pulmonary hypertension is a disorder that may occur in the setting of various underlying medical conditions or as a disease that uniquely affects the pulmonary vasculature 3.
- The classification of pulmonary hypertension has evolved over time, with the introduction of new concepts and terminology, such as pulmonary arterial hypertension (PAH) 3, 4.
- Therapeutic management of PAH has advanced in recent years, with the development of new drugs and treatment strategies 4, 5.