If you ask this neurologist, the heart is an overrated organ. All it does is pump. Over and over. For as long as you live. In an average lifetime, it beats over 2.5 billion times.
Okay, that's pretty cool, actually. Even if it doesn't do all the amazing things the human brain can do, I guess it's important. What it doesn't do is love. That's the brain.
Still, Janis Joplin wrote a pretty damn amazing song with PIECEOF / MYHEART, which in this puzzle is interpreted literally at the end of each of the other theme answers. Thus, ECHOCHAMBER and SAFETYVALVE refer to the two atria and ventricles and the doors between them. TRAFFICARTERY and INTHESAMEVEIN are referring to the vessels which enter and leave the heart. I'm not actually convinced that anyone would refer to them as pieces of the heart medically, but most illustrations include the aorta and superior and inverior vena cava.
Still, it's a lot of theme material, and fine answers as well. In addition, we get the immortal ABBEYROAD and LETSITFLY for colorful fill. I also enjoyed the symmetric geographic answers AFRICA and GENEVA, as well as the historic LASCALA, site of Verdi and Puccini's greatest triumphs.
No complaints here, and it moved quickly enough for a sub-3 minute solve.