  AstroSat spectra of the black hole system GRS 1915+105 during the heartbeat
state (with a varying oscillation period from 150 to 100 secs) were analysed
using a truncated relativistic disc model along with a Comptonization
component. Spectra were fitted for segments of length ~ 24 secs. The
oscillation can be described as coordinated variations of the accretion rate,
Comptonised flux, and the inner disc radius, with the latter ranging from
1.235-5 gravitational radii. Comparison with results from the $\chi$ and
Intermediate states shows that while the accretion rate and the high energy
photon index were similar, the inner disc radius and the fraction of
Comptonised photons were larger for these states than for the heartbeat one.
The coronal efficiency $\eta \equiv L_{ac}/\dot M c^2$, where $L_{ac}$ is the
radiative luminosity generated in the corona is found to be approximately
$\propto \dot M^{-2/3}$ for all the observations. The efficiency decreases with
inner radii for the heartbeat state but has similar values for the $\chi$ and
Intermediate states where the inner radii is larger. The implications of these
results are discussed.
