What is the clinical evidence from this study?

Study design: Observational. Population: Healthy subjects (n=17). Intervention: Real-time cardiac magnetic resonance (CMR) imaging. Primary outcome: Interaction between respiration and left versus right ventricular volumes (p=<0.0001).

January 25, 2014Open Access

Interaction between respiration and right versus left ventricular volumes at rest and during exercise: a real-time cardiac magnetic resonance study

Q: What are the key findings of this study?

Real-time CMR showed that ventricular volumes oscillate with respiratory phase, with RV volumes increasing (RVEDV +18±8%) and LV volumes decreasing during inspiration (P<0.0001 for interaction).

Key Result

Real-time CMR showed that ventricular volumes oscillate with respiratory phase, with RV volumes increasing (RVEDV +18±8%) and LV volumes decreasing during inspiration (P<0.0001 for interaction).

Study Design

Type

Observational (n=17)

Structured PICO

Does the respiratory phase affect right and left ventricular volumes measured by real-time CMR at rest and during exercise in healthy subjects?

Population

17 healthy subjects (8 in a rest cohort, 9 in a separate exercise cohort)

Intervention

Real-time cardiac magnetic resonance (CMR) imaging during normal breathing, breath holding, Valsalva maneuver, and incremental exercise

Comparator

Comparison between respiratory phases (peak inspiration vs. peak expiration)

Outcome

Changes in left ventricular (LV) and right ventricular (RV) end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and eccentricity indexessurrogate

Ventricular volumes oscillate reciprocally with the respiratory phase, highlighting the need to carefully define the exact respiratory time point for accurate interpretation of RV and LV volumes on CMR.

Main Result

p-value: p=<0.0001

Abstract

Breathing-induced changes in intrathoracic pressures influence left ventricular (LV) and right ventricular (RV) volumes, the exact nature and extent of which have not previously been evaluated in humans. We sought to examine this "respiratory pump" using novel real-time cardiac magnetic resonance (CMR) imaging. Eight healthy subjects underwent serial multislice real-time CMR during normal breathing, breath holding, and the Valsalva maneuver. Subsequently, a separate cohort of nine subjects underwent real-time CMR at rest and during incremental exercise. LV and RV end-diastolic volume (EDV) and end-systolic volume (ESV) and diastolic and systolic eccentricity indexes were determined at peak inspiration and expiration. During normal breathing, inspiration resulted in an increase in RV volumes RVEDV: +18 ± 8%, RVESV: +14 ± 12%, and RV stroke volume (SV): +21 ± 10%, P < 0.01 and an opposing decrease in LV volumes (P < 0.0001 for interaction). During end-inspiratory breath holding, RV SV decreased by 9 ± 10% (P = 0.046), whereas LV SV did not change. During the Valsalva maneuver, volumes decreased in both ventricles (RVEDV: -29 ± 11%, RVESV: -16 ± 14%, RV SV: -36 ± 14%, LVEDV: -22 ± 17%, and LV SV: -25 ± 17%, P < 0.01). The reciprocal effect of respiration on LV and RV volumes was maintained throughout exercise. The diastolic and systolic eccentricity indexes were greater during inspiration than during expiration, both at rest and during exercise (P < 0.0001 for both). In conclusion, ventricular volumes oscillate with respiratory phase such that RV and LV volumes are maximal at peak inspiration and expiration, respectively. Thus, interpretation of RV versus LV volumes requires careful definition of the exact respiratory time point for proper interpretation, both at rest and during exercise.