We embed a one-dimensional map describing the atrioventricular conduction delay (originally proposed by M. R. Guevara) into a complex mathematical model of the baroreceptor-cardiac control loop. The baroreflex feedback leads to a qualitative change of cardiac dynamics if the mean atrioventricular conduction delay is increased above normal values. Such an increase is typical for atrioventricular block of first and second degree. We find entrainment and chaotic dynamics between sinoatrial and atrioventricular nodal impulses. For the chaotic regime we observe a strong excitation of 10 s blood pressure oscillations.