A good heart-opening yoga practice can be approached from the standpoint of spiritually opening the heart region, or of physically opening the area of the body where the breath is concentrated. Both sprititual and physical goals can be reached with the same set of postures and the same type of yoga practice.
Heart-Opening Yoga Postures

A specific group of poses targets the area of the heart. These postures create physical space inside the chest by opening and stretching the upper body. In addition to experiencing the increased flexibility and decreased pressure in the chest area, these poses can help one reach a higher level of spiritual awareness with one's body. As you work on these heart-opening yoga postures, don't forget to also concentrate on your breathing. Breathe slowly and deeply to maximize the effect of these postures.

Camel Pose
A modified version of Camel Pose is shown in the top right corner of this page. As you work deeper into Camel Pose, your hands will come to rest on your ankles behind you, further opening up the heart region. An excellent stretch for the chest area, as well as opening the area of the lungs, this pose is a great heart opener. This pose should be worked into slowly, and beginners should not force themselves beyond their limits.

Start by kneeling on the floor, with knees hip-distance apart and the tops of your feet flat on the floor behind you.
Tighten your thighs and your buttocks (but don't lock them) to make sure that your thighs and lower body are perpendicular to the floor.
Gently place your hands, fingers pointing towards the floor, on your lower back and press with your hands.
In this first step, it is important to apply pressure with your hands without letting your lower body form an arc---keep your thighs and below your waist perpendicular to the ground.
Beginners can stick with this version, or slowly work into a version (full Camel Pose) in which your hands come to rest on your ankles or feet. Try this version with your yoga teacher before attempting it on your own.

Backbends
All backbends are heart-opening poses. Backbends should be practiced with a licensed yoga teacher to begin with, and with a spotter if you want to practice the poses at home. Backbends, very similar to Camel Pose, open the front of the upper body, which has a powerful effect on the heart region. You will feel the muscles and tendons between and surrounding your rib cage come farther apart from one another. As you stretch this area, you can take in more and deeper breaths, which is the biggest secret to a happy, healthy, relaxed, yet strong body.

Upward-Facing Dog
Part of the Sun Salutation Sequence, this pose opens the front of the body, whereas Downward-Facing Dog stretches the back of the body. More suitable for beginners than Camel Pose, Upward-Facing Dog can be as deep or as shallow as you can manage, making it a staple for any heart-opening yoga practice. Despite looking simple, this pose has some subtleties best supervised by a yoga teacher. Practice this posture on its own before doing it in the Sun Salutation so that you have time to get this one posture right.

Lying on your stomach, place your hands on the ground beneath your shoulders.
Gently push up, extending the arms, as far as is comfortable.
Try not to lock the elbows or put too much strain on the lower back. If you feel strain, lower the body slightly.
Lift the chin to arc the head back and open the heart area.
One of the biggest challenges is to not tighten the buttocks or cramp up the muscles in the lower back. For these details, a yoga instructor is helpful for correcting your form as you work on the pose. Each beginning yogi will reach a different height with their chest in this pose. Accept the level you can come to, and breathe slowly and deeply to maximize the heart-opening effects of the pose.

Targeted Heart-Opening Yoga Practices

Several hospitals, health centers, and yoga studios teach specialized yoga classes for heart patients, or generally heart-opening yoga classes. Check with local studios and with your doctor's office to find such opportunities in your area. If no similar classes exist, you may consider investing in private yoga lessons or a yoga DVD or two. Shiva Rea's Radiant Heart Yoga combines heart-opening yoga poses into a dynamic flow yoga series to increase your heart rate. Another great DVD, especially for beginners, is the Heart Healthy Peggy Cappy DVD from her Yoga for the Rest of Us series.

As with all yoga, practice mindfully and accept your limits. Check with your doctor before beginning any exercise routine, especially if you are being treated for a heart condition. With your doctor's approval, yoga has the power to open your heart, strengthen your body, lower your heart rate, and help you relax and be less stressed.