Cocker Spaniel with High Vagal Tone

We have a sweet, older American Cocker Spaniel somewhere between 14 & 17 years old (rescue). She had a rough beginning- a late spay & then malignant mammory tumors that were removed twice surgically about 6-7 years ago. She has been on a raw food diet, supplements & some chinese medicine since that time and has been doing fine. Since we've had her (~ 9 years), she's always had a very slow (~40 bpm) but strong heart rate. This has not been a problem for her until recently. Last time we had her teeth cleaned & she was put under, we gathered that they almost lost her & had to inject her w/ something to revive her. Since then she began having what appeared to be mini-seizures. We immediately took her to our vet who determined that her heart was missing beats to the tune of ~3-4 seconds at a time which was what was causing her to "faint". He suggested a cardiologist. The cardiologist put her through a number of tests including the wearing of a heart monitor for a week to record any abnormalities. She also did an atropine test which our girl responded favorably to and was thus diagnosed with High Vagal Tone Syndrome (the brain is not giving the heart the neccessary information). She now takes a drug called propantheline (3.75 mg 3x a day) to increase the heart rate but it does nothing about the pauses. It seems to work intermitantly, she'll have a couple good days where she does not 'faint' but then she'll begin to have what looks like seizures which I wonder if the drug is causing. The 'seizures' cause her to tense her body, fall over if we don't catch her & twitch her muscles & eyes. Afterwords she becomes amped we're told due to adrenaline. This cycle usually goes on for about an hour until she settles again & sleeps. We have three vets (one holistic) & no other solutions to be offered other than acupuncture or pace maker. I've recently come across a natural product (tincture) for epilepsy/seizures that contains:
Passiflora incarnata (Passionflower) Scutellaria laterifolia (Skullcap) Hyoscyamus (30C) Belladonna (30C) Cuprum mettalicum (30C)
Apparently it can be used continuously as a preventive for chronic situations as well as for immediate relief w/acute situations. I would greatly appreciate your take on this or any other information you may have to offer.

The drug you mention has quite an impact on the entire body and has a very long list of other drugs with which it will interact. Although no such list exists for this drug and herbs, it is not because the possibility does not exist, it is just that no research has yet be performed in this area. Therefore, I would strongly recommend that you do not use herbs without one-on-one guidance from aqualified professional who is experienced in the use of herbs with animals and conditions of this sort. In addition, homeopathics in a case such as this would be based on specific constitutional prescribing for your dog, resulting in a recommendation that would fit her unique case history. Therefore, I would not use the product you mention in this instance. I suspect it may be fine for animals not currently on drugs but your cocker spaniel is and that must be taken into account. Please see the website of the Veterinary Botanical Medicine Association (www.vbma.org) or The Academy of Veterinary Homeopathy (www.theavh.org) for a practitioner in your area.
I would suggest that you make sure your dog's diet contains all necessary nutrients; if you haven't already, do check the work of Richard Pitcairn, "Natural Health for Dogs and Cats", "The Complete Herbal Handbook for the Dog and Cat" by Juliette de Bairacli Levy and "The Barf Diet" by Ian Billinghurst for further information and recipes. There is also a supplement powder made by Wysong called "Call of the Wild" that is meant to complete raw food diets;it may be worth a look as well. Good nutrition means a strong body and a strong nervous system (including the vagus nerve and heart). I also would question if there are other ways to keep your dog's teeth clean reather than facing anaesthetic: perhaps raw bones to chew, raw chicken necks to chew (made of cartilage) or even a toothbrush and dog toothpaste.
Lastly, you may want to look at the use of flower essences as they will not interact with her medications. Available at any good health food shop, look for Scleranthus and Rescue Remedy (amde of five essences). Take a 50 ml amber or blue glass dropper bottle and fill it with 50 ml spring water. To that add two drops of the Scleranthus and four drops of the Rescue Remedy. Give your dog one dropperful in her food twice a day. She may also have the diluted essences massaged into the skin on the inside of her earflaps as well as her belly. Most animals find this quite comforting and it may be done as many times as you like per day.