Abstract
SummaryBackgroundTotal heart volume (THV) within the pericardium is not constant throughout the cardiac cycle and THV would intuitively be lowest at end systole. We have, however, observed a phase shift between ventricular outflow and atrial inflow which causes the minimum THV to occur before end systole. The aims were to explain the mechanism of the late‐systolic net inflow to the heart and determine whether this net inflow is affected by increased cardiac output or systolic heart failure.Methods and ResultsHealthy controls (n = 21) and patients with EF<35% (n = 14) underwent magnetic resonance imaging with flow measurements in vessels to and from the heart, and this was repeated in nine controls during 140 μgram kg−1 min−1 adenosine infusion. Minimum THV occurred 78 ± 6 ms before end of systolic ejection (8 ± 1% of the cardiac cycle) in controls. The late‐systolic net inflow was 12·3 ± 1·1 ml or 6·0 ± 0·5% of total stroke volume (TSV). Cardiac output increased 66 ± 8% during adenosine but late‐systolic net inflow to the heart did not change (P = 0·73). In patients with heart failure, late‐systolic net inflow of the heart′s left side was lower (3·4 ± 0·5%) compared to healthy subjects (5·3 ± 0·6%, P = 0·03).ConclusionsHeart size increases before end systole due to a late‐systolic net inflow which is unaffected by increased cardiac output. This may be explained by inertia of blood that flows into the atria generated by ventricular systole. The lower late‐systolic net inflow in patients with systolic heart failure may be a measure of decreased ventricular filling due to decreased systolic function, thus linking systolic to diastolic dysfunction.
Highlights
The total heart volume (THV) has been shown to decrease during systole by 4%–11% in man (Bowman & Kovacs, 2003; Carlsson et al, 2004, 2005; Steding-Ehrenborg et al, 2013a,b)
This may be explained by inertia of blood that flows into the atria generated by ventricular systole
There is a decrease in the content of the pericardial sac during systole, the so-called total heart volume variation (THVV), caused by the difference in flow between blood ejected into the great arteries and the blood drawn into the atria from the caval and pulmonary veins by the atrioventricular plane displacement (AVPD) (Lundback, 1986; Carlsson et al, 2007a,b; Steding-Ehrenborg et al, 2013a,b) (Waters et al, 2005)
Summary
The total heart volume (THV) has been shown to decrease during systole by 4%–11% in man (Bowman & Kovacs, 2003; Carlsson et al, 2004, 2005; Steding-Ehrenborg et al, 2013a,b). The ejecting ventricles manage to eject a greater volume than what the descent of the closed AV-plane pulls into the atria This is performed by inward displacement of the epicardial surface of the ventricles (Waters et al, 2005; Carlsson et al, 2007a,a,b,b). Conclusions Heart size increases before end systole due to a late-systolic net inflow which is unaffected by increased cardiac output. This may be explained by inertia of blood that flows into the atria generated by ventricular systole. The lower latesystolic net inflow in patients with systolic heart failure may be a measure of decreased ventricular filling due to decreased systolic function, linking systolic to diastolic dysfunction
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